28 files changed, 106 insertions, 66 deletions
diff --git a/compiler/rustc_mir_build/src/build/block.rs b/compiler/rustc_mir_build/src/builder/block.rs
index 89e64015bc4..ba63a97de89 100644
--- a/compiler/rustc_mir_build/src/build/block.rs
+++ b/compiler/rustc_mir_build/src/builder/block.rs
@@ -5,9 +5,9 @@ use rustc_middle::{span_bug, ty};
 use rustc_span::Span;
 use tracing::debug;
 
-use crate::build::ForGuard::OutsideGuard;
-use crate::build::matches::{DeclareLetBindings, EmitStorageLive, ScheduleDrops};
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
+use crate::builder::ForGuard::OutsideGuard;
+use crate::builder::matches::{DeclareLetBindings, EmitStorageLive, ScheduleDrops};
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     pub(crate) fn ast_block(
diff --git a/compiler/rustc_mir_build/src/build/cfg.rs b/compiler/rustc_mir_build/src/builder/cfg.rs
index 9c5ee5b0996..cca309115ba 100644
--- a/compiler/rustc_mir_build/src/build/cfg.rs
+++ b/compiler/rustc_mir_build/src/builder/cfg.rs
@@ -4,7 +4,7 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 use tracing::debug;
 
-use crate::build::CFG;
+use crate::builder::CFG;
 
 impl<'tcx> CFG<'tcx> {
     pub(crate) fn block_data(&self, blk: BasicBlock) -> &BasicBlockData<'tcx> {
diff --git a/compiler/rustc_mir_build/src/build/coverageinfo.rs b/compiler/rustc_mir_build/src/builder/coverageinfo.rs
index 52a4a4b4b51..a80bd4f3c80 100644
--- a/compiler/rustc_mir_build/src/build/coverageinfo.rs
+++ b/compiler/rustc_mir_build/src/builder/coverageinfo.rs
@@ -8,8 +8,8 @@ use rustc_middle::thir::{ExprId, ExprKind, Pat, Thir};
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::LocalDefId;
 
-use crate::build::coverageinfo::mcdc::MCDCInfoBuilder;
-use crate::build::{Builder, CFG};
+use crate::builder::coverageinfo::mcdc::MCDCInfoBuilder;
+use crate::builder::{Builder, CFG};
 
 mod mcdc;
 
diff --git a/compiler/rustc_mir_build/src/build/coverageinfo/mcdc.rs b/compiler/rustc_mir_build/src/builder/coverageinfo/mcdc.rs
index 343d4000043..6b4871dc1fc 100644
--- a/compiler/rustc_mir_build/src/build/coverageinfo/mcdc.rs
+++ b/compiler/rustc_mir_build/src/builder/coverageinfo/mcdc.rs
@@ -9,7 +9,7 @@ use rustc_middle::thir::LogicalOp;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::Span;
 
-use crate::build::Builder;
+use crate::builder::Builder;
 use crate::errors::MCDCExceedsConditionLimit;
 
 /// LLVM uses `i16` to represent condition id. Hence `i16::MAX` is the hard limit for number of
diff --git a/compiler/rustc_mir_build/src/build/custom/mod.rs b/compiler/rustc_mir_build/src/builder/custom/mod.rs
index 34cdc288f0b..34cdc288f0b 100644
--- a/compiler/rustc_mir_build/src/build/custom/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/custom/mod.rs
diff --git a/compiler/rustc_mir_build/src/build/custom/parse.rs b/compiler/rustc_mir_build/src/builder/custom/parse.rs
index 538068e1fac..538068e1fac 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse.rs
+++ b/compiler/rustc_mir_build/src/builder/custom/parse.rs
diff --git a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs b/compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs
index 67114efdff5..59f440432eb 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
+++ b/compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs
@@ -9,8 +9,8 @@ use rustc_span::Span;
 use rustc_span::source_map::Spanned;
 
 use super::{PResult, ParseCtxt, parse_by_kind};
-use crate::build::custom::ParseError;
-use crate::build::expr::as_constant::as_constant_inner;
+use crate::builder::custom::ParseError;
+use crate::builder::expr::as_constant::as_constant_inner;
 
 impl<'a, 'tcx> ParseCtxt<'a, 'tcx> {
     pub(crate) fn parse_statement(&self, expr_id: ExprId) -> PResult<StatementKind<'tcx>> {
diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
index 640408cb9c8..177c1e33a83 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
@@ -14,7 +14,7 @@ use rustc_middle::ty::{
 use rustc_middle::{bug, mir, span_bug};
 use tracing::{instrument, trace};
 
-use crate::build::{Builder, parse_float_into_constval};
+use crate::builder::{Builder, parse_float_into_constval};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr`, yielding a compile-time constant. Assumes that
diff --git a/compiler/rustc_mir_build/src/build/expr/as_operand.rs b/compiler/rustc_mir_build/src/builder/expr/as_operand.rs
index 777ff9e68f0..63e9b1dc6cd 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_operand.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_operand.rs
@@ -4,8 +4,8 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use tracing::{debug, instrument};
 
-use crate::build::expr::category::Category;
-use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
+use crate::builder::expr::category::Category;
+use crate::builder::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Construct a temporary lifetime restricted to just the local scope
diff --git a/compiler/rustc_mir_build/src/build/expr/as_place.rs b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
index 70a74910a68..01aec70f437 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
@@ -14,9 +14,9 @@ use rustc_middle::{bug, span_bug};
 use rustc_span::{DesugaringKind, Span};
 use tracing::{debug, instrument, trace};
 
-use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
-use crate::build::expr::category::Category;
-use crate::build::{BlockAnd, BlockAndExtension, Builder, Capture, CaptureMap};
+use crate::builder::ForGuard::{OutsideGuard, RefWithinGuard};
+use crate::builder::expr::category::Category;
+use crate::builder::{BlockAnd, BlockAndExtension, Builder, Capture, CaptureMap};
 
 /// The "outermost" place that holds this value.
 #[derive(Copy, Clone, Debug, PartialEq)]
@@ -68,7 +68,7 @@ pub(crate) enum PlaceBase {
 /// This is used internally when building a place for an expression like `a.b.c`. The fields `b`
 /// and `c` can be progressively pushed onto the place builder that is created when converting `a`.
 #[derive(Clone, Debug, PartialEq)]
-pub(in crate::build) struct PlaceBuilder<'tcx> {
+pub(in crate::builder) struct PlaceBuilder<'tcx> {
     base: PlaceBase,
     projection: Vec<PlaceElem<'tcx>>,
 }
@@ -249,7 +249,7 @@ fn strip_prefix<'a, 'tcx>(
 }
 
 impl<'tcx> PlaceBuilder<'tcx> {
-    pub(in crate::build) fn to_place(&self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
+    pub(in crate::builder) fn to_place(&self, cx: &Builder<'_, 'tcx>) -> Place<'tcx> {
         self.try_to_place(cx).unwrap_or_else(|| match self.base {
             PlaceBase::Local(local) => span_bug!(
                 cx.local_decls[local].source_info.span,
@@ -265,7 +265,7 @@ impl<'tcx> PlaceBuilder<'tcx> {
     }
 
     /// Creates a `Place` or returns `None` if an upvar cannot be resolved
-    pub(in crate::build) fn try_to_place(&self, cx: &Builder<'_, 'tcx>) -> Option<Place<'tcx>> {
+    pub(in crate::builder) fn try_to_place(&self, cx: &Builder<'_, 'tcx>) -> Option<Place<'tcx>> {
         let resolved = self.resolve_upvar(cx);
         let builder = resolved.as_ref().unwrap_or(self);
         let PlaceBase::Local(local) = builder.base else { return None };
@@ -283,7 +283,7 @@ impl<'tcx> PlaceBuilder<'tcx> {
     /// not captured. This can happen because the final mir that will be
     /// generated doesn't require a read for this place. Failures will only
     /// happen inside closures.
-    pub(in crate::build) fn resolve_upvar(
+    pub(in crate::builder) fn resolve_upvar(
         &self,
         cx: &Builder<'_, 'tcx>,
     ) -> Option<PlaceBuilder<'tcx>> {
@@ -647,13 +647,31 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
         match place_ty.kind() {
             ty::Array(_elem_ty, len_const) => {
-                // We know how long an array is, so just use that as a constant
-                // directly -- no locals needed. We do need one statement so
-                // that borrow- and initialization-checking consider it used,
-                // though. FIXME: Do we really *need* to count this as a use?
-                // Could partial array tracking work off something else instead?
-                self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
-                let const_ = Const::from_ty_const(*len_const, usize_ty, self.tcx);
+                let ty_const = if let Some((_, len_ty)) = len_const.try_to_valtree()
+                    && len_ty != self.tcx.types.usize
+                {
+                    // Bad const generics can give us a constant from the type that's
+                    // not actually a `usize`, so in that case give an error instead.
+                    // FIXME: It'd be nice if the type checker made sure this wasn't
+                    // possible, instead.
+                    let err = self.tcx.dcx().span_delayed_bug(
+                        span,
+                        format!(
+                            "Array length should have already been a type error, as it's {len_ty:?}"
+                        ),
+                    );
+                    ty::Const::new_error(self.tcx, err)
+                } else {
+                    // We know how long an array is, so just use that as a constant
+                    // directly -- no locals needed. We do need one statement so
+                    // that borrow- and initialization-checking consider it used,
+                    // though. FIXME: Do we really *need* to count this as a use?
+                    // Could partial array tracking work off something else instead?
+                    self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
+                    *len_const
+                };
+
+                let const_ = Const::from_ty_const(ty_const, usize_ty, self.tcx);
                 Operand::Constant(Box::new(ConstOperand { span, user_ty: None, const_ }))
             }
             ty::Slice(_elem_ty) => {
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
index c66af118453..9961c2488ef 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
@@ -16,9 +16,9 @@ use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Span};
 use tracing::debug;
 
-use crate::build::expr::as_place::PlaceBase;
-use crate::build::expr::category::{Category, RvalueFunc};
-use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
+use crate::builder::expr::as_place::PlaceBase;
+use crate::builder::expr::category::{Category, RvalueFunc};
+use crate::builder::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Returns an rvalue suitable for use until the end of the current
diff --git a/compiler/rustc_mir_build/src/build/expr/as_temp.rs b/compiler/rustc_mir_build/src/builder/expr/as_temp.rs
index 466f67b1ba4..5e3a24e18fb 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_temp.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_temp.rs
@@ -7,8 +7,8 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use tracing::{debug, instrument};
 
-use crate::build::scope::DropKind;
-use crate::build::{BlockAnd, BlockAndExtension, Builder};
+use crate::builder::scope::DropKind;
+use crate::builder::{BlockAnd, BlockAndExtension, Builder};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr` into a fresh temporary. This is used when building
diff --git a/compiler/rustc_mir_build/src/build/expr/category.rs b/compiler/rustc_mir_build/src/builder/expr/category.rs
index e0349e3e3f6..e0349e3e3f6 100644
--- a/compiler/rustc_mir_build/src/build/expr/category.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/category.rs
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/builder/expr/into.rs
index a3d5376dcd4..88f63d4e22c 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/into.rs
@@ -11,9 +11,9 @@ use rustc_middle::ty::CanonicalUserTypeAnnotation;
 use rustc_span::source_map::Spanned;
 use tracing::{debug, instrument};
 
-use crate::build::expr::category::{Category, RvalueFunc};
-use crate::build::matches::DeclareLetBindings;
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, NeedsTemporary};
+use crate::builder::expr::category::{Category, RvalueFunc};
+use crate::builder::matches::DeclareLetBindings;
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder, NeedsTemporary};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Compile `expr`, storing the result into `destination`, which
@@ -367,14 +367,20 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             .collect()
                     }
                     AdtExprBase::DefaultFields(field_types) => {
-                        itertools::zip_eq(field_names, &**field_types)
-                            .map(|(n, ty)| match fields_map.get(&n) {
+                        itertools::zip_eq(field_names, field_types)
+                            .map(|(n, &ty)| match fields_map.get(&n) {
                                 Some(v) => v.clone(),
                                 None => match variant.fields[n].value {
                                     Some(def) => {
-                                        let value = Const::from_unevaluated(this.tcx, def)
-                                            .instantiate(this.tcx, args);
-                                        this.literal_operand(expr_span, value)
+                                        let value = Const::Unevaluated(
+                                            UnevaluatedConst::new(def, args),
+                                            ty,
+                                        );
+                                        Operand::Constant(Box::new(ConstOperand {
+                                            span: expr_span,
+                                            user_ty: None,
+                                            const_: value,
+                                        }))
                                     }
                                     None => {
                                         let name = variant.fields[n].name;
diff --git a/compiler/rustc_mir_build/src/build/expr/mod.rs b/compiler/rustc_mir_build/src/builder/expr/mod.rs
index 3de43a3370f..3de43a3370f 100644
--- a/compiler/rustc_mir_build/src/build/expr/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/mod.rs
diff --git a/compiler/rustc_mir_build/src/build/expr/stmt.rs b/compiler/rustc_mir_build/src/builder/expr/stmt.rs
index 15ee6dd014c..4ae3536d9c2 100644
--- a/compiler/rustc_mir_build/src/build/expr/stmt.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/stmt.rs
@@ -5,8 +5,8 @@ use rustc_middle::thir::*;
 use rustc_span::source_map::Spanned;
 use tracing::debug;
 
-use crate::build::scope::BreakableTarget;
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
+use crate::builder::scope::BreakableTarget;
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Builds a block of MIR statements to evaluate the THIR `expr`.
diff --git a/compiler/rustc_mir_build/src/build/matches/match_pair.rs b/compiler/rustc_mir_build/src/builder/matches/match_pair.rs
index 33fbd7b1a3f..9d59ffc88ba 100644
--- a/compiler/rustc_mir_build/src/build/matches/match_pair.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/match_pair.rs
@@ -2,9 +2,9 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::{self, *};
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
 
-use crate::build::Builder;
-use crate::build::expr::as_place::{PlaceBase, PlaceBuilder};
-use crate::build::matches::{FlatPat, MatchPairTree, TestCase};
+use crate::builder::Builder;
+use crate::builder::expr::as_place::{PlaceBase, PlaceBuilder};
+use crate::builder::matches::{FlatPat, MatchPairTree, TestCase};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Builds and returns [`MatchPairTree`] subtrees, one for each pattern in
@@ -86,7 +86,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 impl<'pat, 'tcx> MatchPairTree<'pat, 'tcx> {
     /// Recursively builds a match pair tree for the given pattern and its
     /// subpatterns.
-    pub(in crate::build) fn for_pattern(
+    pub(in crate::builder) fn for_pattern(
         mut place_builder: PlaceBuilder<'tcx>,
         pattern: &'pat Pat<'tcx>,
         cx: &mut Builder<'_, 'tcx>,
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/builder/matches/mod.rs
index 5791460a6b1..edbe9c69109 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/mod.rs
@@ -18,10 +18,10 @@ use rustc_span::symbol::Symbol;
 use rustc_span::{BytePos, Pos, Span};
 use tracing::{debug, instrument};
 
-use crate::build::ForGuard::{self, OutsideGuard, RefWithinGuard};
-use crate::build::expr::as_place::PlaceBuilder;
-use crate::build::scope::DropKind;
-use crate::build::{
+use crate::builder::ForGuard::{self, OutsideGuard, RefWithinGuard};
+use crate::builder::expr::as_place::PlaceBuilder;
+use crate::builder::scope::DropKind;
+use crate::builder::{
     BlockAnd, BlockAndExtension, Builder, GuardFrame, GuardFrameLocal, LocalsForNode,
 };
 
diff --git a/compiler/rustc_mir_build/src/build/matches/simplify.rs b/compiler/rustc_mir_build/src/builder/matches/simplify.rs
index 5b402604395..ebaed1e431b 100644
--- a/compiler/rustc_mir_build/src/build/matches/simplify.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/simplify.rs
@@ -16,8 +16,8 @@ use std::mem;
 
 use tracing::{debug, instrument};
 
-use crate::build::Builder;
-use crate::build::matches::{MatchPairTree, PatternExtraData, TestCase};
+use crate::builder::Builder;
+use crate::builder::matches::{MatchPairTree, PatternExtraData, TestCase};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Simplify a list of match pairs so they all require a test. Stores relevant bindings and
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/builder/matches/test.rs
index 4f7bbc4ce3e..596d525f5d8 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/test.rs
@@ -20,8 +20,8 @@ use rustc_span::symbol::{Symbol, sym};
 use rustc_span::{DUMMY_SP, Span};
 use tracing::{debug, instrument};
 
-use crate::build::Builder;
-use crate::build::matches::{Candidate, MatchPairTree, Test, TestBranch, TestCase, TestKind};
+use crate::builder::Builder;
+use crate::builder::matches::{Candidate, MatchPairTree, Test, TestBranch, TestCase, TestKind};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Identifies what test is needed to decide if `match_pair` is applicable.
diff --git a/compiler/rustc_mir_build/src/build/matches/util.rs b/compiler/rustc_mir_build/src/builder/matches/util.rs
index 555684ded81..1bd399e511b 100644
--- a/compiler/rustc_mir_build/src/build/matches/util.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/util.rs
@@ -4,9 +4,9 @@ use rustc_middle::ty::Ty;
 use rustc_span::Span;
 use tracing::debug;
 
-use crate::build::Builder;
-use crate::build::expr::as_place::PlaceBase;
-use crate::build::matches::{Binding, Candidate, FlatPat, MatchPairTree, TestCase};
+use crate::builder::Builder;
+use crate::builder::expr::as_place::PlaceBase;
+use crate::builder::matches::{Binding, Candidate, FlatPat, MatchPairTree, TestCase};
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Creates a false edge to `imaginary_target` and a real edge to
diff --git a/compiler/rustc_mir_build/src/build/misc.rs b/compiler/rustc_mir_build/src/builder/misc.rs
index a14dcad6573..a53ae05e84f 100644
--- a/compiler/rustc_mir_build/src/build/misc.rs
+++ b/compiler/rustc_mir_build/src/builder/misc.rs
@@ -7,7 +7,7 @@ use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::debug;
 
-use crate::build::Builder;
+use crate::builder::Builder;
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Adds a new temporary value of type `ty` storing the result of
diff --git a/compiler/rustc_mir_build/src/build/mod.rs b/compiler/rustc_mir_build/src/builder/mod.rs
index f43c29d8f5d..96e4ca3493d 100644
--- a/compiler/rustc_mir_build/src/build/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/mod.rs
@@ -1,3 +1,8 @@
+//! This module used to be named `build`, but that was causing GitHub's
+//! "Go to file" feature to silently ignore all files in the module, probably
+//! because it assumes that "build" is a build-output directory.
+//! See <https://github.com/rust-lang/rust/pull/134365>.
+
 use itertools::Itertools;
 use rustc_abi::{ExternAbi, FieldIdx};
 use rustc_apfloat::Float;
@@ -23,8 +28,8 @@ use rustc_span::symbol::sym;
 use rustc_span::{Span, Symbol};
 
 use super::lints;
-use crate::build::expr::as_place::PlaceBuilder;
-use crate::build::scope::DropKind;
+use crate::builder::expr::as_place::PlaceBuilder;
+use crate::builder::scope::DropKind;
 
 pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
     tcx: TyCtxt<'tcx>,
diff --git a/compiler/rustc_mir_build/src/build/scope.rs b/compiler/rustc_mir_build/src/builder/scope.rs
index 636e47b7ad2..882e29de46d 100644
--- a/compiler/rustc_mir_build/src/build/scope.rs
+++ b/compiler/rustc_mir_build/src/builder/scope.rs
@@ -95,7 +95,7 @@ use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Span};
 use tracing::{debug, instrument};
 
-use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
+use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
 
 #[derive(Debug)]
 pub(crate) struct Scopes<'tcx> {
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index 90be690e034..fc0031616aa 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -18,7 +18,7 @@ use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::symbol::Symbol;
 use rustc_span::{Span, sym};
 
-use crate::build::ExprCategory;
+use crate::builder::ExprCategory;
 use crate::errors::*;
 
 struct UnsafetyVisitor<'a, 'tcx> {
diff --git a/compiler/rustc_mir_build/src/lib.rs b/compiler/rustc_mir_build/src/lib.rs
index 833e5019865..467725841dc 100644
--- a/compiler/rustc_mir_build/src/lib.rs
+++ b/compiler/rustc_mir_build/src/lib.rs
@@ -11,7 +11,10 @@
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
-mod build;
+// The `builder` module used to be named `build`, but that was causing GitHub's
+// "Go to file" feature to silently ignore all files in the module, probably
+// because it assumes that "build" is a build-output directory. See #134365.
+mod builder;
 mod check_tail_calls;
 mod check_unsafety;
 mod errors;
@@ -25,9 +28,9 @@ rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 pub fn provide(providers: &mut Providers) {
     providers.check_match = thir::pattern::check_match;
     providers.lit_to_const = thir::constant::lit_to_const;
-    providers.hooks.build_mir = build::mir_build;
+    providers.hooks.build_mir = builder::mir_build;
     providers.closure_saved_names_of_captured_variables =
-        build::closure_saved_names_of_captured_variables;
+        builder::closure_saved_names_of_captured_variables;
     providers.check_unsafety = check_unsafety::check_unsafety;
     providers.check_tail_calls = check_tail_calls::check_tail_calls;
     providers.thir_body = thir::cx::thir_body;
diff --git a/compiler/rustc_mir_build/src/thir/constant.rs b/compiler/rustc_mir_build/src/thir/constant.rs
index 30b6718683b..ce1c635d1b9 100644
--- a/compiler/rustc_mir_build/src/thir/constant.rs
+++ b/compiler/rustc_mir_build/src/thir/constant.rs
@@ -5,7 +5,7 @@ use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput};
 use rustc_middle::ty::{self, ScalarInt, TyCtxt, TypeVisitableExt as _};
 use tracing::trace;
 
-use crate::build::parse_float_into_scalar;
+use crate::builder::parse_float_into_scalar;
 
 pub(crate) fn lit_to_const<'tcx>(
     tcx: TyCtxt<'tcx>,
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 6770e562d50..ae49b266153 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -25,6 +25,14 @@ use crate::thir::cx::Cx;
 use crate::thir::util::UserAnnotatedTyHelpers;
 
 impl<'tcx> Cx<'tcx> {
+    /// Create a THIR expression for the given HIR expression. This expands all
+    /// adjustments and directly adds the type information from the
+    /// `typeck_results`. See the [dev-guide] for more details.
+    ///
+    /// (The term "mirror" in this case does not refer to "flipped" or
+    /// "reversed".)
+    ///
+    /// [dev-guide]: https://rustc-dev-guide.rust-lang.org/thir.html
     pub(crate) fn mirror_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) -> ExprId {
         // `mirror_expr` is recursing very deep. Make sure the stack doesn't overflow.
         ensure_sufficient_stack(|| self.mirror_expr_inner(expr))
@@ -1189,7 +1197,7 @@ impl<'tcx> Cx<'tcx> {
             .temporary_scope(self.region_scope_tree, closure_expr.hir_id.local_id);
         let var_ty = place.base_ty;
 
-        // The result of capture analysis in `rustc_hir_analysis/check/upvar.rs`represents a captured path
+        // The result of capture analysis in `rustc_hir_typeck/src/upvar.rs` represents a captured path
         // as it's seen for use within the closure and not at the time of closure creation.
         //
         // That is we see expect to see it start from a captured upvar and not something that is local