Rollup merge of #104543 - JhonnyBillM:migrate-codegen-ssa-to-diagnostics-structs-pt3, r=davidtwco

Migrate `codegen_ssa` to diagnostics structs - [Part 3]

Completes migrating `codegen_ssa` module except 2 outstanding errors that depend on other crates:
1. [`rustc_middle::mir::interpret::InterpError`](https://github.com/rust-lang/rust/blob/b6097f2e1b2ca62e188ba53cf43bd66b06b36915/compiler/rustc_middle/src/mir/interpret/error.rs#L475): I saw `rustc_middle` is unassigned, I am open to take this work.

2.  `codegen_llvm`'s use of `fn span_invalid_monomorphization_error`, which I started to replace in the [last commit](https://github.com/rust-lang/rust/commit/9a31b3cdda78a2c0891828254fe9886e0a1cfd16) of this PR, but would like to know the team's preference on how we should keep replacing the other macros:
2.1. Update macros to expect a `Diagnostic`
2.2. Remove macros and expand the code on each use.
See [some examples of the different options in this experimental commit](https://github.com/JhonnyBillM/rust/commit/64aee83e80857dcfa450f0c6e31d5f29c6d577e6)

_Part 2 - https://github.com/rust-lang/rust/pull/103792_

r? ``@davidtwco``
Cc ``@compiler-errors``

15 files changed, 920 insertions, 341 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 4f48506b5af..86e1e50c400 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3890,6 +3890,7 @@ dependencies = [
  "rustc_span",
  "rustc_symbol_mangling",
  "rustc_target",
+ "rustc_type_ir",
  "serde_json",
  "smallvec",
  "snap",
@@ -4024,6 +4025,7 @@ dependencies = [
  "rustc_serialize",
  "rustc_span",
  "rustc_target",
+ "rustc_type_ir",
  "serde",
  "serde_json",
  "termcolor",
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 1ce48f82e1c..680d810f78e 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -8,8 +8,8 @@ use crate::va_arg::emit_va_arg;
 use crate::value::Value;
 
 use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh};
-use rustc_codegen_ssa::common::span_invalid_monomorphization_error;
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
+use rustc_codegen_ssa::errors::{ExpectedPointerMutability, InvalidMonomorphization};
 use rustc_codegen_ssa::mir::operand::OperandRef;
 use rustc_codegen_ssa::mir::place::PlaceRef;
 use rustc_codegen_ssa::traits::*;
@@ -284,15 +284,11 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                         _ => bug!(),
                     },
                     None => {
-                        span_invalid_monomorphization_error(
-                            tcx.sess,
+                        tcx.sess.emit_err(InvalidMonomorphization::BasicIntegerType {
                             span,
-                            &format!(
-                                "invalid monomorphization of `{}` intrinsic: \
-                                      expected basic integer type, found `{}`",
-                                name, ty
-                            ),
-                        );
+                            name,
+                            ty,
+                        });
                         return;
                     }
                 }
@@ -838,40 +834,24 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     llret_ty: &'ll Type,
     span: Span,
 ) -> Result<&'ll Value, ()> {
-    // macros for error handling:
-    #[allow(unused_macro_rules)]
-    macro_rules! emit_error {
-        ($msg: tt) => {
-            emit_error!($msg, )
-        };
-        ($msg: tt, $($fmt: tt)*) => {
-            span_invalid_monomorphization_error(
-                bx.sess(), span,
-                &format!(concat!("invalid monomorphization of `{}` intrinsic: ", $msg),
-                         name, $($fmt)*));
-        }
-    }
-
     macro_rules! return_error {
-        ($($fmt: tt)*) => {
-            {
-                emit_error!($($fmt)*);
-                return Err(());
-            }
-        }
+        ($diag: expr) => {{
+            bx.sess().emit_err($diag);
+            return Err(());
+        }};
     }
 
     macro_rules! require {
-        ($cond: expr, $($fmt: tt)*) => {
+        ($cond: expr, $diag: expr) => {
             if !$cond {
-                return_error!($($fmt)*);
+                return_error!($diag);
             }
         };
     }
 
     macro_rules! require_simd {
-        ($ty: expr, $position: expr) => {
-            require!($ty.is_simd(), "expected SIMD {} type, found non-SIMD `{}`", $position, $ty)
+        ($ty: expr, $diag: expr) => {
+            require!($ty.is_simd(), $diag)
         };
     }
 
@@ -881,7 +861,11 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     let arg_tys = sig.inputs();
 
     if name == sym::simd_select_bitmask {
-        require_simd!(arg_tys[1], "argument");
+        require_simd!(
+            arg_tys[1],
+            InvalidMonomorphization::SimdArgument { span, name, ty: arg_tys[1] }
+        );
+
         let (len, _) = arg_tys[1].simd_size_and_type(bx.tcx());
 
         let expected_int_bits = (len.max(8) - 1).next_power_of_two();
@@ -902,12 +886,13 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 let ptr = bx.pointercast(place.llval, bx.cx.type_ptr_to(int_ty));
                 bx.load(int_ty, ptr, Align::ONE)
             }
-            _ => return_error!(
-                "invalid bitmask `{}`, expected `u{}` or `[u8; {}]`",
+            _ => return_error!(InvalidMonomorphization::InvalidBitmask {
+                span,
+                name,
                 mask_ty,
                 expected_int_bits,
                 expected_bytes
-            ),
+            }),
         };
 
         let i1 = bx.type_i1();
@@ -919,7 +904,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     }
 
     // every intrinsic below takes a SIMD vector as its first argument
-    require_simd!(arg_tys[0], "input");
+    require_simd!(arg_tys[0], InvalidMonomorphization::SimdInput { span, name, ty: arg_tys[0] });
     let in_ty = arg_tys[0];
 
     let comparison = match name {
@@ -934,23 +919,24 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
 
     let (in_len, in_elem) = arg_tys[0].simd_size_and_type(bx.tcx());
     if let Some(cmp_op) = comparison {
-        require_simd!(ret_ty, "return");
+        require_simd!(ret_ty, InvalidMonomorphization::SimdReturn { span, name, ty: ret_ty });
 
         let (out_len, out_ty) = ret_ty.simd_size_and_type(bx.tcx());
+
         require!(
             in_len == out_len,
-            "expected return type with length {} (same as input type `{}`), \
-             found `{}` with length {}",
-            in_len,
-            in_ty,
-            ret_ty,
-            out_len
+            InvalidMonomorphization::ReturnLengthInputType {
+                span,
+                name,
+                in_len,
+                in_ty,
+                ret_ty,
+                out_len
+            }
         );
         require!(
             bx.type_kind(bx.element_type(llret_ty)) == TypeKind::Integer,
-            "expected return type with integer elements, found `{}` with non-integer `{}`",
-            ret_ty,
-            out_ty
+            InvalidMonomorphization::ReturnIntegerType { span, name, ret_ty, out_ty }
         );
 
         return Ok(compare_simd_types(
@@ -975,10 +961,11 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                         span_bug!(span, "could not evaluate shuffle index array length")
                     })
                 }
-                _ => return_error!(
-                    "simd_shuffle index must be an array of `u32`, got `{}`",
-                    args[2].layout.ty
-                ),
+                _ => return_error!(InvalidMonomorphization::SimdShuffle {
+                    span,
+                    name,
+                    ty: args[2].layout.ty
+                }),
             }
         } else {
             stripped.parse().unwrap_or_else(|_| {
@@ -986,23 +973,15 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             })
         };
 
-        require_simd!(ret_ty, "return");
+        require_simd!(ret_ty, InvalidMonomorphization::SimdReturn { span, name, ty: ret_ty });
         let (out_len, out_ty) = ret_ty.simd_size_and_type(bx.tcx());
         require!(
             out_len == n,
-            "expected return type of length {}, found `{}` with length {}",
-            n,
-            ret_ty,
-            out_len
+            InvalidMonomorphization::ReturnLength { span, name, in_len: n, ret_ty, out_len }
         );
         require!(
             in_elem == out_ty,
-            "expected return element type `{}` (element of input `{}`), \
-             found `{}` with element type `{}`",
-            in_elem,
-            in_ty,
-            ret_ty,
-            out_ty
+            InvalidMonomorphization::ReturnElement { span, name, in_elem, in_ty, ret_ty, out_ty }
         );
 
         let total_len = u128::from(in_len) * 2;
@@ -1015,15 +994,20 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 let val = bx.const_get_elt(vector, i as u64);
                 match bx.const_to_opt_u128(val, true) {
                     None => {
-                        emit_error!("shuffle index #{} is not a constant", arg_idx);
+                        bx.sess().emit_err(InvalidMonomorphization::ShuffleIndexNotConstant {
+                            span,
+                            name,
+                            arg_idx,
+                        });
                         None
                     }
                     Some(idx) if idx >= total_len => {
-                        emit_error!(
-                            "shuffle index #{} is out of bounds (limit {})",
+                        bx.sess().emit_err(InvalidMonomorphization::ShuffleIndexOutOfBounds {
+                            span,
+                            name,
                             arg_idx,
-                            total_len
-                        );
+                            total_len,
+                        });
                         None
                     }
                     Some(idx) => Some(bx.const_i32(idx as i32)),
@@ -1044,10 +1028,13 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     if name == sym::simd_insert {
         require!(
             in_elem == arg_tys[2],
-            "expected inserted type `{}` (element of input `{}`), found `{}`",
-            in_elem,
-            in_ty,
-            arg_tys[2]
+            InvalidMonomorphization::InsertedType {
+                span,
+                name,
+                in_elem,
+                in_ty,
+                out_ty: arg_tys[2]
+            }
         );
         return Ok(bx.insert_element(
             args[0].immediate(),
@@ -1058,10 +1045,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     if name == sym::simd_extract {
         require!(
             ret_ty == in_elem,
-            "expected return type `{}` (element of input `{}`), found `{}`",
-            in_elem,
-            in_ty,
-            ret_ty
+            InvalidMonomorphization::ReturnType { span, name, in_elem, in_ty, ret_ty }
         );
         return Ok(bx.extract_element(args[0].immediate(), args[1].immediate()));
     }
@@ -1069,17 +1053,18 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     if name == sym::simd_select {
         let m_elem_ty = in_elem;
         let m_len = in_len;
-        require_simd!(arg_tys[1], "argument");
+        require_simd!(
+            arg_tys[1],
+            InvalidMonomorphization::SimdArgument { span, name, ty: arg_tys[1] }
+        );
         let (v_len, _) = arg_tys[1].simd_size_and_type(bx.tcx());
         require!(
             m_len == v_len,
-            "mismatched lengths: mask length `{}` != other vector length `{}`",
-            m_len,
-            v_len
+            InvalidMonomorphization::MismatchedLengths { span, name, m_len, v_len }
         );
         match m_elem_ty.kind() {
             ty::Int(_) => {}
-            _ => return_error!("mask element type is `{}`, expected `i_`", m_elem_ty),
+            _ => return_error!(InvalidMonomorphization::MaskType { span, name, ty: m_elem_ty }),
         }
         // truncate the mask to a vector of i1s
         let i1 = bx.type_i1();
@@ -1111,11 +1096,12 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 args[0].immediate(),
                 i.bit_width().unwrap_or_else(|| bx.data_layout().pointer_size.bits()),
             ),
-            _ => return_error!(
-                "vector argument `{}`'s element type `{}`, expected integer element type",
+            _ => return_error!(InvalidMonomorphization::VectorArgument {
+                span,
+                name,
                 in_ty,
                 in_elem
-            ),
+            }),
         };
 
         // Shift the MSB to the right by "in_elem_bitwidth - 1" into the first bit position.
@@ -1150,12 +1136,13 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                 let ptr = bx.pointercast(ptr, bx.cx.type_ptr_to(array_ty));
                 return Ok(bx.load(array_ty, ptr, Align::ONE));
             }
-            _ => return_error!(
-                "cannot return `{}`, expected `u{}` or `[u8; {}]`",
+            _ => return_error!(InvalidMonomorphization::CannotReturn {
+                span,
+                name,
                 ret_ty,
                 expected_int_bits,
                 expected_bytes
-            ),
+            }),
         }
     }
 
@@ -1168,25 +1155,11 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         span: Span,
         args: &[OperandRef<'tcx, &'ll Value>],
     ) -> Result<&'ll Value, ()> {
-        #[allow(unused_macro_rules)]
-        macro_rules! emit_error {
-            ($msg: tt) => {
-                emit_error!($msg, )
-            };
-            ($msg: tt, $($fmt: tt)*) => {
-                span_invalid_monomorphization_error(
-                    bx.sess(), span,
-                    &format!(concat!("invalid monomorphization of `{}` intrinsic: ", $msg),
-                             name, $($fmt)*));
-            }
-        }
         macro_rules! return_error {
-            ($($fmt: tt)*) => {
-                {
-                    emit_error!($($fmt)*);
-                    return Err(());
-                }
-            }
+            ($diag: expr) => {{
+                bx.sess().emit_err($diag);
+                return Err(());
+            }};
         }
 
         let (elem_ty_str, elem_ty) = if let ty::Float(f) = in_elem.kind() {
@@ -1194,16 +1167,15 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             match f.bit_width() {
                 32 => ("f32", elem_ty),
                 64 => ("f64", elem_ty),
-                _ => {
-                    return_error!(
-                        "unsupported element type `{}` of floating-point vector `{}`",
-                        f.name_str(),
-                        in_ty
-                    );
-                }
+                _ => return_error!(InvalidMonomorphization::FloatingPointVector {
+                    span,
+                    name,
+                    f_ty: *f,
+                    in_ty,
+                }),
             }
         } else {
-            return_error!("`{}` is not a floating-point type", in_ty);
+            return_error!(InvalidMonomorphization::FloatingPointType { span, name, in_ty });
         };
 
         let vec_ty = bx.type_vector(elem_ty, in_len);
@@ -1225,7 +1197,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             sym::simd_fsqrt => ("sqrt", bx.type_func(&[vec_ty], vec_ty)),
             sym::simd_round => ("round", bx.type_func(&[vec_ty], vec_ty)),
             sym::simd_trunc => ("trunc", bx.type_func(&[vec_ty], vec_ty)),
-            _ => return_error!("unrecognized intrinsic `{}`", name),
+            _ => return_error!(InvalidMonomorphization::UnrecognizedIntrinsic { span, name }),
         };
         let llvm_name = &format!("llvm.{0}.v{1}{2}", intr_name, in_len, elem_ty_str);
         let f = bx.declare_cfn(llvm_name, llvm::UnnamedAddr::No, fn_ty);
@@ -1319,37 +1291,48 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         // * M: any integer width is supported, will be truncated to i1
 
         // All types must be simd vector types
-        require_simd!(in_ty, "first");
-        require_simd!(arg_tys[1], "second");
-        require_simd!(arg_tys[2], "third");
-        require_simd!(ret_ty, "return");
+        require_simd!(in_ty, InvalidMonomorphization::SimdFirst { span, name, ty: in_ty });
+        require_simd!(
+            arg_tys[1],
+            InvalidMonomorphization::SimdSecond { span, name, ty: arg_tys[1] }
+        );
+        require_simd!(
+            arg_tys[2],
+            InvalidMonomorphization::SimdThird { span, name, ty: arg_tys[2] }
+        );
+        require_simd!(ret_ty, InvalidMonomorphization::SimdReturn { span, name, ty: ret_ty });
 
         // Of the same length:
         let (out_len, _) = arg_tys[1].simd_size_and_type(bx.tcx());
         let (out_len2, _) = arg_tys[2].simd_size_and_type(bx.tcx());
         require!(
             in_len == out_len,
-            "expected {} argument with length {} (same as input type `{}`), \
-             found `{}` with length {}",
-            "second",
-            in_len,
-            in_ty,
-            arg_tys[1],
-            out_len
+            InvalidMonomorphization::SecondArgumentLength {
+                span,
+                name,
+                in_len,
+                in_ty,
+                arg_ty: arg_tys[1],
+                out_len
+            }
         );
         require!(
             in_len == out_len2,
-            "expected {} argument with length {} (same as input type `{}`), \
-             found `{}` with length {}",
-            "third",
-            in_len,
-            in_ty,
-            arg_tys[2],
-            out_len2
+            InvalidMonomorphization::ThirdArgumentLength {
+                span,
+                name,
+                in_len,
+                in_ty,
+                arg_ty: arg_tys[2],
+                out_len: out_len2
+            }
         );
 
         // The return type must match the first argument type
-        require!(ret_ty == in_ty, "expected return type `{}`, found `{}`", in_ty, ret_ty);
+        require!(
+            ret_ty == in_ty,
+            InvalidMonomorphization::ExpectedReturnType { span, name, in_ty, ret_ty }
+        );
 
         // This counts how many pointers
         fn ptr_count(t: Ty<'_>) -> usize {
@@ -1376,15 +1359,15 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             _ => {
                 require!(
                     false,
-                    "expected element type `{}` of second argument `{}` \
-                        to be a pointer to the element type `{}` of the first \
-                        argument `{}`, found `{}` != `*_ {}`",
-                    element_ty1,
-                    arg_tys[1],
-                    in_elem,
-                    in_ty,
-                    element_ty1,
-                    in_elem
+                    InvalidMonomorphization::ExpectedElementType {
+                        span,
+                        name,
+                        expected_element: element_ty1,
+                        second_arg: arg_tys[1],
+                        in_elem,
+                        in_ty,
+                        mutability: ExpectedPointerMutability::Not,
+                    }
                 );
                 unreachable!();
             }
@@ -1400,10 +1383,12 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             _ => {
                 require!(
                     false,
-                    "expected element type `{}` of third argument `{}` \
-                                 to be a signed integer type",
-                    element_ty2,
-                    arg_tys[2]
+                    InvalidMonomorphization::ThirdArgElementType {
+                        span,
+                        name,
+                        expected_element: element_ty2,
+                        third_arg: arg_tys[2]
+                    }
                 );
             }
         }
@@ -1452,32 +1437,40 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
         // * M: any integer width is supported, will be truncated to i1
 
         // All types must be simd vector types
-        require_simd!(in_ty, "first");
-        require_simd!(arg_tys[1], "second");
-        require_simd!(arg_tys[2], "third");
+        require_simd!(in_ty, InvalidMonomorphization::SimdFirst { span, name, ty: in_ty });
+        require_simd!(
+            arg_tys[1],
+            InvalidMonomorphization::SimdSecond { span, name, ty: arg_tys[1] }
+        );
+        require_simd!(
+            arg_tys[2],
+            InvalidMonomorphization::SimdThird { span, name, ty: arg_tys[2] }
+        );
 
         // Of the same length:
         let (element_len1, _) = arg_tys[1].simd_size_and_type(bx.tcx());
         let (element_len2, _) = arg_tys[2].simd_size_and_type(bx.tcx());
         require!(
             in_len == element_len1,
-            "expected {} argument with length {} (same as input type `{}`), \
-            found `{}` with length {}",
-            "second",
-            in_len,
-            in_ty,
-            arg_tys[1],
-            element_len1
+            InvalidMonomorphization::SecondArgumentLength {
+                span,
+                name,
+                in_len,
+                in_ty,
+                arg_ty: arg_tys[1],
+                out_len: element_len1
+            }
         );
         require!(
             in_len == element_len2,
-            "expected {} argument with length {} (same as input type `{}`), \
-            found `{}` with length {}",
-            "third",
-            in_len,
-            in_ty,
-            arg_tys[2],
-            element_len2
+            InvalidMonomorphization::ThirdArgumentLength {
+                span,
+                name,
+                in_len,
+                in_ty,
+                arg_ty: arg_tys[2],
+                out_len: element_len2
+            }
         );
 
         // This counts how many pointers
@@ -1508,15 +1501,15 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             _ => {
                 require!(
                     false,
-                    "expected element type `{}` of second argument `{}` \
-                        to be a pointer to the element type `{}` of the first \
-                        argument `{}`, found `{}` != `*mut {}`",
-                    element_ty1,
-                    arg_tys[1],
-                    in_elem,
-                    in_ty,
-                    element_ty1,
-                    in_elem
+                    InvalidMonomorphization::ExpectedElementType {
+                        span,
+                        name,
+                        expected_element: element_ty1,
+                        second_arg: arg_tys[1],
+                        in_elem,
+                        in_ty,
+                        mutability: ExpectedPointerMutability::Mut,
+                    }
                 );
                 unreachable!();
             }
@@ -1531,10 +1524,12 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             _ => {
                 require!(
                     false,
-                    "expected element type `{}` of third argument `{}` \
-                         be a signed integer type",
-                    element_ty2,
-                    arg_tys[2]
+                    InvalidMonomorphization::ThirdArgElementType {
+                        span,
+                        name,
+                        expected_element: element_ty2,
+                        third_arg: arg_tys[2]
+                    }
                 );
             }
         }
@@ -1581,10 +1576,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             if name == sym::$name {
                 require!(
                     ret_ty == in_elem,
-                    "expected return type `{}` (element of input `{}`), found `{}`",
-                    in_elem,
-                    in_ty,
-                    ret_ty
+                    InvalidMonomorphization::ReturnType { span, name, in_elem, in_ty, ret_ty }
                 );
                 return match in_elem.kind() {
                     ty::Int(_) | ty::Uint(_) => {
@@ -1607,25 +1599,28 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
                                 32 => bx.const_real(bx.type_f32(), $identity),
                                 64 => bx.const_real(bx.type_f64(), $identity),
                                 v => return_error!(
-                                    r#"
-unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
-                                    sym::$name,
-                                    in_ty,
-                                    in_elem,
-                                    v,
-                                    ret_ty
+                                    InvalidMonomorphization::UnsupportedSymbolOfSize {
+                                        span,
+                                        name,
+                                        symbol: sym::$name,
+                                        in_ty,
+                                        in_elem,
+                                        size: v,
+                                        ret_ty
+                                    }
                                 ),
                             }
                         };
                         Ok(bx.$float_reduce(acc, args[0].immediate()))
                     }
-                    _ => return_error!(
-                        "unsupported {} from `{}` with element `{}` to `{}`",
-                        sym::$name,
+                    _ => return_error!(InvalidMonomorphization::UnsupportedSymbol {
+                        span,
+                        name,
+                        symbol: sym::$name,
                         in_ty,
                         in_elem,
                         ret_ty
-                    ),
+                    }),
                 };
             }
         };
@@ -1653,22 +1648,20 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
             if name == sym::$name {
                 require!(
                     ret_ty == in_elem,
-                    "expected return type `{}` (element of input `{}`), found `{}`",
-                    in_elem,
-                    in_ty,
-                    ret_ty
+                    InvalidMonomorphization::ReturnType { span, name, in_elem, in_ty, ret_ty }
                 );
                 return match in_elem.kind() {
                     ty::Int(_i) => Ok(bx.$int_red(args[0].immediate(), true)),
                     ty::Uint(_u) => Ok(bx.$int_red(args[0].immediate(), false)),
                     ty::Float(_f) => Ok(bx.$float_red(args[0].immediate())),
-                    _ => return_error!(
-                        "unsupported {} from `{}` with element `{}` to `{}`",
-                        sym::$name,
+                    _ => return_error!(InvalidMonomorphization::UnsupportedSymbol {
+                        span,
+                        name,
+                        symbol: sym::$name,
                         in_ty,
                         in_elem,
                         ret_ty
-                    ),
+                    }),
                 };
             }
         };
@@ -1686,22 +1679,20 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                 let input = if !$boolean {
                     require!(
                         ret_ty == in_elem,
-                        "expected return type `{}` (element of input `{}`), found `{}`",
-                        in_elem,
-                        in_ty,
-                        ret_ty
+                        InvalidMonomorphization::ReturnType { span, name, in_elem, in_ty, ret_ty }
                     );
                     args[0].immediate()
                 } else {
                     match in_elem.kind() {
                         ty::Int(_) | ty::Uint(_) => {}
-                        _ => return_error!(
-                            "unsupported {} from `{}` with element `{}` to `{}`",
-                            sym::$name,
+                        _ => return_error!(InvalidMonomorphization::UnsupportedSymbol {
+                            span,
+                            name,
+                            symbol: sym::$name,
                             in_ty,
                             in_elem,
                             ret_ty
-                        ),
+                        }),
                     }
 
                     // boolean reductions operate on vectors of i1s:
@@ -1714,13 +1705,14 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                         let r = bx.$red(input);
                         Ok(if !$boolean { r } else { bx.zext(r, bx.type_bool()) })
                     }
-                    _ => return_error!(
-                        "unsupported {} from `{}` with element `{}` to `{}`",
-                        sym::$name,
+                    _ => return_error!(InvalidMonomorphization::UnsupportedSymbol {
+                        span,
+                        name,
+                        symbol: sym::$name,
                         in_ty,
                         in_elem,
                         ret_ty
-                    ),
+                    }),
                 };
             }
         };
@@ -1733,16 +1725,18 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
     bitwise_red!(simd_reduce_any: vector_reduce_or, true);
 
     if name == sym::simd_cast_ptr {
-        require_simd!(ret_ty, "return");
+        require_simd!(ret_ty, InvalidMonomorphization::SimdReturn { span, name, ty: ret_ty });
         let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
         require!(
             in_len == out_len,
-            "expected return type with length {} (same as input type `{}`), \
-                  found `{}` with length {}",
-            in_len,
-            in_ty,
-            ret_ty,
-            out_len
+            InvalidMonomorphization::ReturnLengthInputType {
+                span,
+                name,
+                in_len,
+                in_ty,
+                ret_ty,
+                out_len
+            }
         );
 
         match in_elem.kind() {
@@ -1751,9 +1745,14 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                     bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
                 });
                 assert!(!check_sized); // we are in codegen, so we shouldn't see these types
-                require!(metadata.is_unit(), "cannot cast fat pointer `{}`", in_elem)
+                require!(
+                    metadata.is_unit(),
+                    InvalidMonomorphization::CastFatPointer { span, name, ty: in_elem }
+                );
+            }
+            _ => {
+                return_error!(InvalidMonomorphization::ExpectedPointer { span, name, ty: in_elem })
             }
-            _ => return_error!("expected pointer, got `{}`", in_elem),
         }
         match out_elem.kind() {
             ty::RawPtr(p) => {
@@ -1761,9 +1760,14 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                     bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
                 });
                 assert!(!check_sized); // we are in codegen, so we shouldn't see these types
-                require!(metadata.is_unit(), "cannot cast to fat pointer `{}`", out_elem)
+                require!(
+                    metadata.is_unit(),
+                    InvalidMonomorphization::CastFatPointer { span, name, ty: out_elem }
+                );
+            }
+            _ => {
+                return_error!(InvalidMonomorphization::ExpectedPointer { span, name, ty: out_elem })
             }
-            _ => return_error!("expected pointer, got `{}`", out_elem),
         }
 
         if in_elem == out_elem {
@@ -1774,66 +1778,76 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
     }
 
     if name == sym::simd_expose_addr {
-        require_simd!(ret_ty, "return");
+        require_simd!(ret_ty, InvalidMonomorphization::SimdReturn { span, name, ty: ret_ty });
         let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
         require!(
             in_len == out_len,
-            "expected return type with length {} (same as input type `{}`), \
-                  found `{}` with length {}",
-            in_len,
-            in_ty,
-            ret_ty,
-            out_len
+            InvalidMonomorphization::ReturnLengthInputType {
+                span,
+                name,
+                in_len,
+                in_ty,
+                ret_ty,
+                out_len
+            }
         );
 
         match in_elem.kind() {
             ty::RawPtr(_) => {}
-            _ => return_error!("expected pointer, got `{}`", in_elem),
+            _ => {
+                return_error!(InvalidMonomorphization::ExpectedPointer { span, name, ty: in_elem })
+            }
         }
         match out_elem.kind() {
             ty::Uint(ty::UintTy::Usize) => {}
-            _ => return_error!("expected `usize`, got `{}`", out_elem),
+            _ => return_error!(InvalidMonomorphization::ExpectedUsize { span, name, ty: out_elem }),
         }
 
         return Ok(bx.ptrtoint(args[0].immediate(), llret_ty));
     }
 
     if name == sym::simd_from_exposed_addr {
-        require_simd!(ret_ty, "return");
+        require_simd!(ret_ty, InvalidMonomorphization::SimdReturn { span, name, ty: ret_ty });
         let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
         require!(
             in_len == out_len,
-            "expected return type with length {} (same as input type `{}`), \
-                  found `{}` with length {}",
-            in_len,
-            in_ty,
-            ret_ty,
-            out_len
+            InvalidMonomorphization::ReturnLengthInputType {
+                span,
+                name,
+                in_len,
+                in_ty,
+                ret_ty,
+                out_len
+            }
         );
 
         match in_elem.kind() {
             ty::Uint(ty::UintTy::Usize) => {}
-            _ => return_error!("expected `usize`, got `{}`", in_elem),
+            _ => return_error!(InvalidMonomorphization::ExpectedUsize { span, name, ty: in_elem }),
         }
         match out_elem.kind() {
             ty::RawPtr(_) => {}
-            _ => return_error!("expected pointer, got `{}`", out_elem),
+            _ => {
+                return_error!(InvalidMonomorphization::ExpectedPointer { span, name, ty: out_elem })
+            }
         }
 
         return Ok(bx.inttoptr(args[0].immediate(), llret_ty));
     }
 
     if name == sym::simd_cast || name == sym::simd_as {
-        require_simd!(ret_ty, "return");
+        require_simd!(ret_ty, InvalidMonomorphization::SimdReturn { span, name, ty: ret_ty });
         let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
         require!(
             in_len == out_len,
-            "expected return type with length {} (same as input type `{}`), \
-                  found `{}` with length {}",
-            in_len,
-            in_ty,
-            ret_ty,
-            out_len
+            InvalidMonomorphization::ReturnLengthInputType {
+                span,
+                name,
+                in_len,
+                in_ty,
+                ret_ty,
+                out_len
+            }
         );
         // casting cares about nominal type, not just structural type
         if in_elem == out_elem {
@@ -1912,11 +1926,14 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
         }
         require!(
             false,
-            "unsupported cast from `{}` with element `{}` to `{}` with element `{}`",
-            in_ty,
-            in_elem,
-            ret_ty,
-            out_elem
+            InvalidMonomorphization::UnsupportedCast {
+                span,
+                name,
+                in_ty,
+                in_elem,
+                ret_ty,
+                out_elem
+            }
         );
     }
     macro_rules! arith_binary {
@@ -1928,10 +1945,10 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                     })*
                     _ => {},
                 }
-                require!(false,
-                         "unsupported operation on `{}` with element `{}`",
-                         in_ty,
-                         in_elem)
+                require!(
+                    false,
+                    InvalidMonomorphization::UnsupportedOperation { span, name, in_ty, in_elem }
+                );
             })*
         }
     }
@@ -1959,10 +1976,10 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
                     })*
                     _ => {},
                 }
-                require!(false,
-                         "unsupported operation on `{}` with element `{}`",
-                         in_ty,
-                         in_elem)
+                require!(
+                    false,
+                    InvalidMonomorphization::UnsupportedOperation { span, name, in_ty, in_elem }
+                );
             })*
         }
     }
@@ -2000,12 +2017,12 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
             ty::Int(i) => (true, i.bit_width().unwrap_or(ptr_bits), bx.cx.type_int_from_ty(i)),
             ty::Uint(i) => (false, i.bit_width().unwrap_or(ptr_bits), bx.cx.type_uint_from_ty(i)),
             _ => {
-                return_error!(
-                    "expected element type `{}` of vector type `{}` \
-                     to be a signed or unsigned integer type",
-                    arg_tys[0].simd_size_and_type(bx.tcx()).1,
-                    arg_tys[0]
-                );
+                return_error!(InvalidMonomorphization::ExpectedVectorElementType {
+                    span,
+                    name,
+                    expected_element: arg_tys[0].simd_size_and_type(bx.tcx()).1,
+                    vector_type: arg_tys[0]
+                });
             }
         };
         let llvm_intrinsic = &format!(
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 345174fb595..d1ad687e6ae 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -27,6 +27,7 @@ rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_span = { path = "../rustc_span" }
 rustc_middle = { path = "../rustc_middle" }
+rustc_type_ir = { path = "../rustc_type_ir" }
 rustc_attr = { path = "../rustc_attr" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }
 rustc_data_structures = { path = "../rustc_data_structures" }
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 5d9b6c9870d..8ca7103ed48 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -2616,7 +2616,7 @@ fn add_static_crate<'a>(
             sess.target.no_builtins || !codegen_results.crate_info.is_no_builtins.contains(&cnum);
 
         let mut archive = archive_builder_builder.new_archive_builder(sess);
-        if let Err(e) = archive.add_archive(
+        if let Err(error) = archive.add_archive(
             cratepath,
             Box::new(move |f| {
                 if f == METADATA_FILENAME {
@@ -2656,7 +2656,7 @@ fn add_static_crate<'a>(
                 false
             }),
         ) {
-            sess.fatal(&format!("failed to build archive from rlib: {}", e));
+            sess.emit_fatal(errors::RlibArchiveBuildFailure { error });
         }
         if archive.build(&dst) {
             link_upstream(&dst);
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 8b34be38580..d318c15d342 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -5,6 +5,7 @@ use crate::back::write::{
     submit_post_lto_module_to_llvm, submit_pre_lto_module_to_llvm, ComputedLtoType, OngoingCodegen,
 };
 use crate::common::{IntPredicate, RealPredicate, TypeKind};
+use crate::errors;
 use crate::meth;
 use crate::mir;
 use crate::mir::operand::OperandValue;
@@ -451,10 +452,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         let Some(llfn) = cx.declare_c_main(llfty) else {
             // FIXME: We should be smart and show a better diagnostic here.
             let span = cx.tcx().def_span(rust_main_def_id);
-            cx.sess()
-                .struct_span_err(span, "entry symbol `main` declared multiple times")
-                .help("did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead")
-                .emit();
+            cx.sess().emit_err(errors::MultipleMainFunctions { span });
             cx.sess().abort_if_errors();
             bug!();
         };
@@ -595,8 +593,8 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
                 &metadata,
                 &exported_symbols::metadata_symbol_name(tcx),
             );
-            if let Err(err) = std::fs::write(&file_name, data) {
-                tcx.sess.fatal(&format!("error writing metadata object file: {}", err));
+            if let Err(error) = std::fs::write(&file_name, data) {
+                tcx.sess.emit_fatal(errors::MetadataObjectFileWrite { error });
             }
             Some(CompiledModule {
                 name: metadata_cgu_name,
@@ -815,11 +813,7 @@ impl CrateInfo {
         let subsystem = tcx.sess.first_attr_value_str_by_name(crate_attrs, sym::windows_subsystem);
         let windows_subsystem = subsystem.map(|subsystem| {
             if subsystem != sym::windows && subsystem != sym::console {
-                tcx.sess.fatal(&format!(
-                    "invalid windows subsystem `{}`, only \
-                                     `windows` and `console` are allowed",
-                    subsystem
-                ));
+                tcx.sess.emit_fatal(errors::InvalidWindowsSubsystem { subsystem });
             }
             subsystem.to_string()
         });
diff --git a/compiler/rustc_codegen_ssa/src/common.rs b/compiler/rustc_codegen_ssa/src/common.rs
index 71f9179d02c..e1abb73a504 100644
--- a/compiler/rustc_codegen_ssa/src/common.rs
+++ b/compiler/rustc_codegen_ssa/src/common.rs
@@ -1,10 +1,8 @@
 #![allow(non_camel_case_types)]
 
-use rustc_errors::struct_span_err;
 use rustc_hir::LangItem;
 use rustc_middle::mir::interpret::ConstValue;
 use rustc_middle::ty::{self, layout::TyAndLayout, Ty, TyCtxt};
-use rustc_session::Session;
 use rustc_span::Span;
 
 use crate::base;
@@ -193,10 +191,6 @@ pub fn shift_mask_val<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     }
 }
 
-pub fn span_invalid_monomorphization_error(a: &Session, b: Span, c: &str) {
-    struct_span_err!(a, b, E0511, "{}", c).emit();
-}
-
 pub fn asm_const_to_str<'tcx>(
     tcx: TyCtxt<'tcx>,
     sp: Span,
diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
index 3ae6c531b44..1599ccbb259 100644
--- a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
+++ b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
@@ -93,6 +93,7 @@ fn push_debuginfo_type_name<'tcx>(
                     Err(e) => {
                         // Computing the layout can still fail here, e.g. if the target architecture
                         // cannot represent the type. See https://github.com/rust-lang/rust/issues/94961.
+                        // FIXME: migrate once `rustc_middle::mir::interpret::InterpError` is translatable.
                         tcx.sess.fatal(&format!("{}", e));
                     }
                 }
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index 277612c30fc..d81252653df 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -6,7 +6,9 @@ use rustc_errors::{
     IntoDiagnosticArg,
 };
 use rustc_macros::Diagnostic;
+use rustc_middle::ty::Ty;
 use rustc_span::{Span, Symbol};
+use rustc_type_ir::FloatTy;
 use std::borrow::Cow;
 use std::io::Error;
 use std::path::{Path, PathBuf};
@@ -549,3 +551,432 @@ pub struct ExpectedUsedSymbol {
     #[primary_span]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_multiple_main_functions)]
+#[help]
+pub struct MultipleMainFunctions {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_metadata_object_file_write)]
+pub struct MetadataObjectFileWrite {
+    pub error: Error,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_invalid_windows_subsystem)]
+pub struct InvalidWindowsSubsystem {
+    pub subsystem: Symbol,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_erroneous_constant)]
+pub struct ErroneousConstant {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_polymorphic_constant_too_generic)]
+pub struct PolymorphicConstantTooGeneric {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_shuffle_indices_evaluation)]
+pub struct ShuffleIndicesEvaluation {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_missing_memory_ordering)]
+pub struct MissingMemoryOrdering;
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_unknown_atomic_ordering)]
+pub struct UnknownAtomicOrdering;
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_atomic_compare_exchange)]
+pub struct AtomicCompareExchange;
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_unknown_atomic_operation)]
+pub struct UnknownAtomicOperation;
+
+#[derive(Diagnostic)]
+pub enum InvalidMonomorphization<'tcx> {
+    #[diag(codegen_ssa_invalid_monomorphization_basic_integer_type, code = "E0511")]
+    BasicIntegerType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_basic_float_type, code = "E0511")]
+    BasicFloatType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_float_to_int_unchecked, code = "E0511")]
+    FloatToIntUnchecked {
+        #[primary_span]
+        span: Span,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_floating_point_vector, code = "E0511")]
+    FloatingPointVector {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        f_ty: FloatTy,
+        in_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_floating_point_type, code = "E0511")]
+    FloatingPointType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_unrecognized_intrinsic, code = "E0511")]
+    UnrecognizedIntrinsic {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_simd_argument, code = "E0511")]
+    SimdArgument {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_simd_input, code = "E0511")]
+    SimdInput {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_simd_first, code = "E0511")]
+    SimdFirst {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_simd_second, code = "E0511")]
+    SimdSecond {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_simd_third, code = "E0511")]
+    SimdThird {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_simd_return, code = "E0511")]
+    SimdReturn {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_invalid_bitmask, code = "E0511")]
+    InvalidBitmask {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        mask_ty: Ty<'tcx>,
+        expected_int_bits: u64,
+        expected_bytes: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_return_length_input_type, code = "E0511")]
+    ReturnLengthInputType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_len: u64,
+        in_ty: Ty<'tcx>,
+        ret_ty: Ty<'tcx>,
+        out_len: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_second_argument_length, code = "E0511")]
+    SecondArgumentLength {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_len: u64,
+        in_ty: Ty<'tcx>,
+        arg_ty: Ty<'tcx>,
+        out_len: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_third_argument_length, code = "E0511")]
+    ThirdArgumentLength {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_len: u64,
+        in_ty: Ty<'tcx>,
+        arg_ty: Ty<'tcx>,
+        out_len: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_return_integer_type, code = "E0511")]
+    ReturnIntegerType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ret_ty: Ty<'tcx>,
+        out_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_simd_shuffle, code = "E0511")]
+    SimdShuffle {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_return_length, code = "E0511")]
+    ReturnLength {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_len: u64,
+        ret_ty: Ty<'tcx>,
+        out_len: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_return_element, code = "E0511")]
+    ReturnElement {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_elem: Ty<'tcx>,
+        in_ty: Ty<'tcx>,
+        ret_ty: Ty<'tcx>,
+        out_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_shuffle_index_not_constant, code = "E0511")]
+    ShuffleIndexNotConstant {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        arg_idx: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_shuffle_index_out_of_bounds, code = "E0511")]
+    ShuffleIndexOutOfBounds {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        arg_idx: u64,
+        total_len: u128,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_inserted_type, code = "E0511")]
+    InsertedType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_elem: Ty<'tcx>,
+        in_ty: Ty<'tcx>,
+        out_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_return_type, code = "E0511")]
+    ReturnType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_elem: Ty<'tcx>,
+        in_ty: Ty<'tcx>,
+        ret_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_expected_return_type, code = "E0511")]
+    ExpectedReturnType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_ty: Ty<'tcx>,
+        ret_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_mismatched_lengths, code = "E0511")]
+    MismatchedLengths {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        m_len: u64,
+        v_len: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_mask_type, code = "E0511")]
+    MaskType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_vector_argument, code = "E0511")]
+    VectorArgument {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_ty: Ty<'tcx>,
+        in_elem: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_cannot_return, code = "E0511")]
+    CannotReturn {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ret_ty: Ty<'tcx>,
+        expected_int_bits: u64,
+        expected_bytes: u64,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_expected_element_type, code = "E0511")]
+    ExpectedElementType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        expected_element: Ty<'tcx>,
+        second_arg: Ty<'tcx>,
+        in_elem: Ty<'tcx>,
+        in_ty: Ty<'tcx>,
+        mutability: ExpectedPointerMutability,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_third_arg_element_type, code = "E0511")]
+    ThirdArgElementType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        expected_element: Ty<'tcx>,
+        third_arg: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_unsupported_symbol_of_size, code = "E0511")]
+    UnsupportedSymbolOfSize {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        symbol: Symbol,
+        in_ty: Ty<'tcx>,
+        in_elem: Ty<'tcx>,
+        size: u64,
+        ret_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_unsupported_symbol, code = "E0511")]
+    UnsupportedSymbol {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        symbol: Symbol,
+        in_ty: Ty<'tcx>,
+        in_elem: Ty<'tcx>,
+        ret_ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_cast_fat_pointer, code = "E0511")]
+    CastFatPointer {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_expected_pointer, code = "E0511")]
+    ExpectedPointer {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_expected_usize, code = "E0511")]
+    ExpectedUsize {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        ty: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_unsupported_cast, code = "E0511")]
+    UnsupportedCast {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_ty: Ty<'tcx>,
+        in_elem: Ty<'tcx>,
+        ret_ty: Ty<'tcx>,
+        out_elem: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_unsupported_operation, code = "E0511")]
+    UnsupportedOperation {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        in_ty: Ty<'tcx>,
+        in_elem: Ty<'tcx>,
+    },
+
+    #[diag(codegen_ssa_invalid_monomorphization_expected_vector_element_type, code = "E0511")]
+    ExpectedVectorElementType {
+        #[primary_span]
+        span: Span,
+        name: Symbol,
+        expected_element: Ty<'tcx>,
+        vector_type: Ty<'tcx>,
+    },
+}
+
+pub enum ExpectedPointerMutability {
+    Mut,
+    Not,
+}
+
+impl IntoDiagnosticArg for ExpectedPointerMutability {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        match self {
+            ExpectedPointerMutability::Mut => DiagnosticArgValue::Str(Cow::Borrowed("*mut")),
+            ExpectedPointerMutability::Not => DiagnosticArgValue::Str(Cow::Borrowed("*_")),
+        }
+    }
+}
diff --git a/compiler/rustc_codegen_ssa/src/mir/constant.rs b/compiler/rustc_codegen_ssa/src/mir/constant.rs
index 53ff3c24096..14fe84a146d 100644
--- a/compiler/rustc_codegen_ssa/src/mir/constant.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/constant.rs
@@ -1,3 +1,4 @@
+use crate::errors;
 use crate::mir::operand::OperandRef;
 use crate::traits::*;
 use rustc_middle::mir;
@@ -44,10 +45,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         self.cx.tcx().const_eval_resolve(ty::ParamEnv::reveal_all(), uv, None).map_err(|err| {
             match err {
                 ErrorHandled::Reported(_) => {
-                    self.cx.tcx().sess.span_err(constant.span, "erroneous constant encountered");
+                    self.cx.tcx().sess.emit_err(errors::ErroneousConstant { span: constant.span });
                 }
                 ErrorHandled::TooGeneric => {
-                    span_bug!(constant.span, "codegen encountered polymorphic constant: {:?}", err);
+                    self.cx
+                        .tcx()
+                        .sess
+                        .diagnostic()
+                        .emit_bug(errors::PolymorphicConstantTooGeneric { span: constant.span });
                 }
             }
             err
@@ -87,7 +92,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 (llval, c.ty())
             })
             .unwrap_or_else(|_| {
-                bx.tcx().sess.span_err(span, "could not evaluate shuffle_indices at compile time");
+                bx.tcx().sess.emit_err(errors::ShuffleIndicesEvaluation { span });
                 // We've errored, so we don't have to produce working code.
                 let ty = self.monomorphize(ty);
                 let llty = bx.backend_type(bx.layout_of(ty));
diff --git a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
index a75609260ed..766dc74cbbb 100644
--- a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
@@ -1,7 +1,9 @@
 use super::operand::{OperandRef, OperandValue};
 use super::place::PlaceRef;
 use super::FunctionCx;
-use crate::common::{span_invalid_monomorphization_error, IntPredicate};
+use crate::common::IntPredicate;
+use crate::errors;
+use crate::errors::InvalidMonomorphization;
 use crate::glue;
 use crate::meth;
 use crate::traits::*;
@@ -305,15 +307,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         _ => bug!(),
                     },
                     None => {
-                        span_invalid_monomorphization_error(
-                            bx.tcx().sess,
-                            span,
-                            &format!(
-                                "invalid monomorphization of `{}` intrinsic: \
-                                      expected basic integer type, found `{}`",
-                                name, ty
-                            ),
-                        );
+                        bx.tcx().sess.emit_err(InvalidMonomorphization::BasicIntegerType { span, name, ty });
                         return;
                     }
                 }
@@ -329,15 +323,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         _ => bug!(),
                     },
                     None => {
-                        span_invalid_monomorphization_error(
-                            bx.tcx().sess,
-                            span,
-                            &format!(
-                                "invalid monomorphization of `{}` intrinsic: \
-                                      expected basic float type, found `{}`",
-                                name, arg_tys[0]
-                            ),
-                        );
+                        bx.tcx().sess.emit_err(InvalidMonomorphization::BasicFloatType { span, name, ty: arg_tys[0] });
                         return;
                     }
                 }
@@ -345,29 +331,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
             sym::float_to_int_unchecked => {
                 if float_type_width(arg_tys[0]).is_none() {
-                    span_invalid_monomorphization_error(
-                        bx.tcx().sess,
-                        span,
-                        &format!(
-                            "invalid monomorphization of `float_to_int_unchecked` \
-                                  intrinsic: expected basic float type, \
-                                  found `{}`",
-                            arg_tys[0]
-                        ),
-                    );
+                    bx.tcx().sess.emit_err(InvalidMonomorphization::FloatToIntUnchecked { span, ty: arg_tys[0] });
                     return;
                 }
                 let Some((_width, signed)) = int_type_width_signed(ret_ty, bx.tcx()) else {
-                    span_invalid_monomorphization_error(
-                        bx.tcx().sess,
-                        span,
-                        &format!(
-                            "invalid monomorphization of `float_to_int_unchecked` \
-                                    intrinsic:  expected basic integer type, \
-                                    found `{}`",
-                            ret_ty
-                        ),
-                    );
+                    bx.tcx().sess.emit_err(InvalidMonomorphization::FloatToIntUnchecked { span, ty: ret_ty });
                     return;
                 };
                 if signed {
@@ -402,7 +370,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 use crate::common::{AtomicRmwBinOp, SynchronizationScope};
 
                 let Some((instruction, ordering)) = atomic.split_once('_') else {
-                    bx.sess().fatal("Atomic intrinsic missing memory ordering");
+                    bx.sess().emit_fatal(errors::MissingMemoryOrdering);
                 };
 
                 let parse_ordering = |bx: &Bx, s| match s {
@@ -412,25 +380,17 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     "release" => Release,
                     "acqrel" => AcquireRelease,
                     "seqcst" => SequentiallyConsistent,
-                    _ => bx.sess().fatal("unknown ordering in atomic intrinsic"),
+                    _ => bx.sess().emit_fatal(errors::UnknownAtomicOrdering),
                 };
 
                 let invalid_monomorphization = |ty| {
-                    span_invalid_monomorphization_error(
-                        bx.tcx().sess,
-                        span,
-                        &format!(
-                            "invalid monomorphization of `{}` intrinsic: \
-                                  expected basic integer type, found `{}`",
-                            name, ty
-                        ),
-                    );
+                    bx.tcx().sess.emit_err(InvalidMonomorphization::BasicIntegerType { span, name, ty });
                 };
 
                 match instruction {
                     "cxchg" | "cxchgweak" => {
                         let Some((success, failure)) = ordering.split_once('_') else {
-                            bx.sess().fatal("Atomic compare-exchange intrinsic missing failure memory ordering");
+                            bx.sess().emit_fatal(errors::AtomicCompareExchange);
                         };
                         let ty = substs.type_at(0);
                         if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
@@ -529,7 +489,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             "min" => AtomicRmwBinOp::AtomicMin,
                             "umax" => AtomicRmwBinOp::AtomicUMax,
                             "umin" => AtomicRmwBinOp::AtomicUMin,
-                            _ => bx.sess().fatal("unknown atomic operation"),
+                            _ => bx.sess().emit_fatal(errors::UnknownAtomicOperation),
                         };
 
                         let ty = substs.type_at(0);
diff --git a/compiler/rustc_error_messages/locales/en-US/codegen_ssa.ftl b/compiler/rustc_error_messages/locales/en-US/codegen_ssa.ftl
index f97943b9bd7..c8c7afb5f91 100644
--- a/compiler/rustc_error_messages/locales/en-US/codegen_ssa.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/codegen_ssa.ftl
@@ -192,3 +192,102 @@ codegen_ssa_unknown_archive_kind =
     Don't know how to build archive of type: {$kind}
 
 codegen_ssa_expected_used_symbol = expected `used`, `used(compiler)` or `used(linker)`
+
+codegen_ssa_multiple_main_functions = entry symbol `main` declared multiple times
+    .help = did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead
+
+codegen_ssa_metadata_object_file_write = error writing metadata object file: {$error}
+
+codegen_ssa_invalid_windows_subsystem = invalid windows subsystem `{$subsystem}`, only `windows` and `console` are allowed
+
+codegen_ssa_erroneous_constant = erroneous constant encountered
+
+codegen_ssa_shuffle_indices_evaluation = could not evaluate shuffle_indices at compile time
+
+codegen_ssa_missing_memory_ordering = Atomic intrinsic missing memory ordering
+
+codegen_ssa_unknown_atomic_ordering = unknown ordering in atomic intrinsic
+
+codegen_ssa_atomic_compare_exchange = Atomic compare-exchange intrinsic missing failure memory ordering
+
+codegen_ssa_unknown_atomic_operation = unknown atomic operation
+
+codegen_ssa_invalid_monomorphization_basic_integer_type = invalid monomorphization of `{$name}` intrinsic: expected basic integer type, found `{$ty}`
+
+codegen_ssa_invalid_monomorphization_basic_float_type = invalid monomorphization of `{$name}` intrinsic: expected basic float type, found `{$ty}`
+
+codegen_ssa_invalid_monomorphization_float_to_int_unchecked = invalid monomorphization of `float_to_int_unchecked` intrinsic: expected basic float type, found `{$ty}`
+
+codegen_ssa_invalid_monomorphization_floating_point_vector = invalid monomorphization of `{$name}` intrinsic: unsupported element type `{$f_ty}` of floating-point vector `{$in_ty}`
+
+codegen_ssa_invalid_monomorphization_floating_point_type = invalid monomorphization of `{$name}` intrinsic: `{$in_ty}` is not a floating-point type
+
+codegen_ssa_invalid_monomorphization_unrecognized_intrinsic = invalid monomorphization of `{$name}` intrinsic: unrecognized intrinsic `{$name}`
+
+codegen_ssa_invalid_monomorphization_simd_argument = invalid monomorphization of `{$name}` intrinsic: expected SIMD argument type, found non-SIMD `{$ty}`
+
+codegen_ssa_invalid_monomorphization_simd_input = invalid monomorphization of `{$name}` intrinsic: expected SIMD input type, found non-SIMD `{$ty}`
+
+codegen_ssa_invalid_monomorphization_simd_first = invalid monomorphization of `{$name}` intrinsic: expected SIMD first type, found non-SIMD `{$ty}`
+
+codegen_ssa_invalid_monomorphization_simd_second = invalid monomorphization of `{$name}` intrinsic: expected SIMD second type, found non-SIMD `{$ty}`
+
+codegen_ssa_invalid_monomorphization_simd_third = invalid monomorphization of `{$name}` intrinsic: expected SIMD third type, found non-SIMD `{$ty}`
+
+codegen_ssa_invalid_monomorphization_simd_return = invalid monomorphization of `{$name}` intrinsic: expected SIMD return type, found non-SIMD `{$ty}`
+
+codegen_ssa_invalid_monomorphization_invalid_bitmask = invalid monomorphization of `{$name}` intrinsic: invalid bitmask `{$mask_ty}`, expected `u{$expected_int_bits}` or `[u8; {$expected_bytes}]`
+
+codegen_ssa_polymorphic_constant_too_generic = codegen encountered polymorphic constant: TooGeneric
+
+codegen_ssa_invalid_monomorphization_return_length_input_type = invalid monomorphization of `{$name}` intrinsic: expected return type with length {$in_len} (same as input type `{$in_ty}`), found `{$ret_ty}` with length {$out_len}
+
+codegen_ssa_invalid_monomorphization_second_argument_length = invalid monomorphization of `{$name}` intrinsic: expected second argument with length {$in_len} (same as input type `{$in_ty}`), found `{$arg_ty}` with length {$out_len}
+
+codegen_ssa_invalid_monomorphization_third_argument_length = invalid monomorphization of `{$name}` intrinsic: expected third argument with length {$in_len} (same as input type `{$in_ty}`), found `{$arg_ty}` with length {$out_len}
+
+codegen_ssa_invalid_monomorphization_return_integer_type = invalid monomorphization of `{$name}` intrinsic: expected return type with integer elements, found `{$ret_ty}` with non-integer `{$out_ty}`
+
+codegen_ssa_invalid_monomorphization_simd_shuffle = invalid monomorphization of `{$name}` intrinsic: simd_shuffle index must be an array of `u32`, got `{$ty}`
+
+codegen_ssa_invalid_monomorphization_return_length = invalid monomorphization of `{$name}` intrinsic: expected return type of length {$in_len}, found `{$ret_ty}` with length {$out_len}
+
+codegen_ssa_invalid_monomorphization_return_element = invalid monomorphization of `{$name}` intrinsic: expected return element type `{$in_elem}` (element of input `{$in_ty}`), found `{$ret_ty}` with element type `{$out_ty}`
+
+codegen_ssa_invalid_monomorphization_shuffle_index_not_constant = invalid monomorphization of `{$name}` intrinsic: shuffle index #{$arg_idx} is not a constant
+
+codegen_ssa_invalid_monomorphization_shuffle_index_out_of_bounds = invalid monomorphization of `{$name}` intrinsic: shuffle index #{$arg_idx} is out of bounds (limit {$total_len})
+
+codegen_ssa_invalid_monomorphization_inserted_type = invalid monomorphization of `{$name}` intrinsic: expected inserted type `{$in_elem}` (element of input `{$in_ty}`), found `{$out_ty}`
+
+codegen_ssa_invalid_monomorphization_return_type = invalid monomorphization of `{$name}` intrinsic: expected return type `{$in_elem}` (element of input `{$in_ty}`), found `{$ret_ty}`
+
+codegen_ssa_invalid_monomorphization_expected_return_type = invalid monomorphization of `{$name}` intrinsic: expected return type `{$in_ty}`, found `{$ret_ty}`
+
+codegen_ssa_invalid_monomorphization_mismatched_lengths = invalid monomorphization of `{$name}` intrinsic: mismatched lengths: mask length `{$m_len}` != other vector length `{$v_len}`
+
+codegen_ssa_invalid_monomorphization_mask_type = invalid monomorphization of `{$name}` intrinsic: mask element type is `{$ty}`, expected `i_`
+
+codegen_ssa_invalid_monomorphization_vector_argument = invalid monomorphization of `{$name}` intrinsic: vector argument `{$in_ty}`'s element type `{$in_elem}`, expected integer element type
+
+codegen_ssa_invalid_monomorphization_cannot_return = invalid monomorphization of `{$name}` intrinsic: cannot return `{$ret_ty}`, expected `u{$expected_int_bits}` or `[u8; {$expected_bytes}]`
+
+codegen_ssa_invalid_monomorphization_expected_element_type = invalid monomorphization of `{$name}` intrinsic: expected element type `{$expected_element}` of second argument `{$second_arg}` to be a pointer to the element type `{$in_elem}` of the first argument `{$in_ty}`, found `{$expected_element}` != `{$mutability} {$in_elem}`
+
+codegen_ssa_invalid_monomorphization_third_arg_element_type = invalid monomorphization of `{$name}` intrinsic: expected element type `{$expected_element}` of third argument `{$third_arg}` to be a signed integer type
+
+codegen_ssa_invalid_monomorphization_unsupported_symbol_of_size = invalid monomorphization of `{$name}` intrinsic: unsupported {$symbol} from `{$in_ty}` with element `{$in_elem}` of size `{$size}` to `{$ret_ty}`
+
+codegen_ssa_invalid_monomorphization_unsupported_symbol = invalid monomorphization of `{$name}` intrinsic: unsupported {$symbol} from `{$in_ty}` with element `{$in_elem}` to `{$ret_ty}`
+
+codegen_ssa_invalid_monomorphization_cast_fat_pointer = invalid monomorphization of `{$name}` intrinsic: cannot cast fat pointer `{$ty}`
+
+codegen_ssa_invalid_monomorphization_expected_pointer = invalid monomorphization of `{$name}` intrinsic: expected pointer, got `{$ty}`
+
+codegen_ssa_invalid_monomorphization_expected_usize = invalid monomorphization of `{$name}` intrinsic: expected `usize`, got `{$ty}`
+
+codegen_ssa_invalid_monomorphization_unsupported_cast = invalid monomorphization of `{$name}` intrinsic: unsupported cast from `{$in_ty}` with element `{$in_elem}` to `{$ret_ty}` with element `{$out_elem}`
+
+codegen_ssa_invalid_monomorphization_unsupported_operation = invalid monomorphization of `{$name}` intrinsic: unsupported operation on `{$in_ty}` with element `{$in_elem}`
+
+codegen_ssa_invalid_monomorphization_expected_vector_element_type = invalid monomorphization of `{$name}` intrinsic: expected element type `{$expected_element}` of vector type `{$vector_type}` to be a signed or unsigned integer type
diff --git a/compiler/rustc_errors/Cargo.toml b/compiler/rustc_errors/Cargo.toml
index dee7a31ec20..cadd53fbd83 100644
--- a/compiler/rustc_errors/Cargo.toml
+++ b/compiler/rustc_errors/Cargo.toml
@@ -17,6 +17,7 @@ rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_target = { path = "../rustc_target" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_lint_defs = { path = "../rustc_lint_defs" }
+rustc_type_ir = { path = "../rustc_type_ir" }
 unicode-width = "0.1.4"
 termcolor = "1.0"
 annotate-snippets = "0.9"
diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index a2ed988643f..cbfee582d87 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -1,7 +1,7 @@
 use crate::diagnostic::IntoDiagnosticArg;
 use crate::{
     Diagnostic, DiagnosticId, DiagnosticMessage, DiagnosticStyledString, ErrorGuaranteed,
-    SubdiagnosticMessage,
+    ExplicitBug, SubdiagnosticMessage,
 };
 use crate::{Handler, Level, MultiSpan, StashKey};
 use rustc_lint_defs::Applicability;
@@ -12,6 +12,7 @@ use std::borrow::Cow;
 use std::fmt::{self, Debug};
 use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};
+use std::panic;
 use std::thread::panicking;
 
 /// Trait implemented by error types. This should not be implemented manually. Instead, use
@@ -308,6 +309,58 @@ impl EmissionGuarantee for Noted {
     }
 }
 
+/// Marker type which enables implementation of `create_bug` and `emit_bug` functions for
+/// bug struct diagnostics.
+#[derive(Copy, Clone)]
+pub struct Bug;
+
+impl<'a> DiagnosticBuilder<'a, Bug> {
+    /// Convenience function for internal use, clients should use one of the
+    /// `struct_*` methods on [`Handler`].
+    #[track_caller]
+    pub(crate) fn new_bug(handler: &'a Handler, message: impl Into<DiagnosticMessage>) -> Self {
+        let diagnostic = Diagnostic::new_with_code(Level::Bug, None, message);
+        Self::new_diagnostic_bug(handler, diagnostic)
+    }
+
+    /// Creates a new `DiagnosticBuilder` with an already constructed
+    /// diagnostic.
+    pub(crate) fn new_diagnostic_bug(handler: &'a Handler, diagnostic: Diagnostic) -> Self {
+        debug!("Created new diagnostic bug");
+        Self {
+            inner: DiagnosticBuilderInner {
+                state: DiagnosticBuilderState::Emittable(handler),
+                diagnostic: Box::new(diagnostic),
+            },
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl EmissionGuarantee for Bug {
+    fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self {
+        match db.inner.state {
+            // First `.emit()` call, the `&Handler` is still available.
+            DiagnosticBuilderState::Emittable(handler) => {
+                db.inner.state = DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation;
+
+                handler.emit_diagnostic(&mut db.inner.diagnostic);
+            }
+            // `.emit()` was previously called, disallowed from repeating it.
+            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
+        }
+        // Then panic. No need to return the marker type.
+        panic::panic_any(ExplicitBug);
+    }
+
+    fn make_diagnostic_builder(
+        handler: &Handler,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, Self> {
+        DiagnosticBuilder::new_bug(handler, msg)
+    }
+}
+
 impl<'a> DiagnosticBuilder<'a, !> {
     /// Convenience function for internal use, clients should use one of the
     /// `struct_*` methods on [`Handler`].
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index 628cb90903f..794b6efcc2b 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -9,6 +9,7 @@ use rustc_span::edition::Edition;
 use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent, Symbol};
 use rustc_target::abi::TargetDataLayoutErrors;
 use rustc_target::spec::{PanicStrategy, SplitDebuginfo, StackProtector, TargetTriple};
+use rustc_type_ir as type_ir;
 use std::borrow::Cow;
 use std::fmt;
 use std::num::ParseIntError;
@@ -170,6 +171,12 @@ impl IntoDiagnosticArg for ast::token::TokenKind {
     }
 }
 
+impl IntoDiagnosticArg for type_ir::FloatTy {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Borrowed(self.name_str()))
+    }
+}
+
 impl IntoDiagnosticArg for Level {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         DiagnosticArgValue::Str(Cow::Borrowed(match self {
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 621704335e4..b4d23e96f8f 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -1133,6 +1133,20 @@ impl Handler {
         self.create_fatal(fatal).emit()
     }
 
+    pub fn create_bug<'a>(
+        &'a self,
+        bug: impl IntoDiagnostic<'a, diagnostic_builder::Bug>,
+    ) -> DiagnosticBuilder<'a, diagnostic_builder::Bug> {
+        bug.into_diagnostic(self)
+    }
+
+    pub fn emit_bug<'a>(
+        &'a self,
+        bug: impl IntoDiagnostic<'a, diagnostic_builder::Bug>,
+    ) -> diagnostic_builder::Bug {
+        self.create_bug(bug).emit()
+    }
+
     fn emit_diag_at_span(
         &self,
         mut diag: Diagnostic,