Split check_cast to a separate file

2 files changed, 184 insertions, 152 deletions

diff --git a/src/librustc_typeck/check/cast.rs b/src/librustc_typeck/check/cast.rs
new file mode 100644
index 00000000000..b35e3c800fc
--- /dev/null
+++ b/src/librustc_typeck/check/cast.rs
@@ -0,0 +1,179 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Code for type-checking cast expressions.
+
+use super::coercion;
+use super::demand;
+use super::FnCtxt;
+use super::structurally_resolved_type;
+
+use lint;
+use middle::infer;
+use middle::ty;
+use middle::ty::Ty;
+use syntax::ast;
+use syntax::codemap::Span;
+
+/// Reifies a cast check to be checked once we have full type information for
+/// a function context.
+pub struct CastCheck<'tcx> {
+    expr: ast::Expr,
+    expr_ty: Ty<'tcx>,
+    cast_ty: Ty<'tcx>,
+    span: Span,
+}
+
+impl<'tcx> CastCheck<'tcx> {
+    pub fn new(expr: ast::Expr, expr_ty: Ty<'tcx>, cast_ty: Ty<'tcx>, span: Span)
+               -> CastCheck<'tcx> {
+        CastCheck {
+            expr: expr,
+            expr_ty: expr_ty,
+            cast_ty: cast_ty,
+            span: span,
+        }
+    }
+}
+
+pub fn check_cast<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, cast: &CastCheck<'tcx>) {
+    fn cast_through_integer_err<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
+                                          span: Span,
+                                          t_1: Ty<'tcx>,
+                                          t_e: Ty<'tcx>) {
+        fcx.type_error_message(span, |actual| {
+            format!("illegal cast; cast through an \
+                    integer first: `{}` as `{}`",
+                    actual,
+                    fcx.infcx().ty_to_string(t_1))
+        }, t_e, None);
+    }
+
+    let span = cast.span;
+    let e = &cast.expr;
+    let t_e = structurally_resolved_type(fcx, span, cast.expr_ty);
+    let t_1 = structurally_resolved_type(fcx, span, cast.cast_ty);
+
+    // Check for trivial casts.
+    if !ty::type_has_ty_infer(t_1) {
+        if let Ok(()) = coercion::mk_assignty(fcx, e, t_e, t_1) {
+            if ty::type_is_numeric(t_1) && ty::type_is_numeric(t_e) {
+                fcx.tcx().sess.add_lint(lint::builtin::TRIVIAL_NUMERIC_CASTS,
+                                        e.id,
+                                        span,
+                                        format!("trivial numeric cast: `{}` as `{}`. Cast can be \
+                                                 replaced by coercion, this might require type \
+                                                 ascription or a temporary variable",
+                                                fcx.infcx().ty_to_string(t_e),
+                                                fcx.infcx().ty_to_string(t_1)));
+            } else {
+                fcx.tcx().sess.add_lint(lint::builtin::TRIVIAL_CASTS,
+                                        e.id,
+                                        span,
+                                        format!("trivial cast: `{}` as `{}`. Cast can be \
+                                                 replaced by coercion, this might require type \
+                                                 ascription or a temporary variable",
+                                                fcx.infcx().ty_to_string(t_e),
+                                                fcx.infcx().ty_to_string(t_1)));
+            }
+            return;
+        }
+    }
+
+    let t_e_is_bare_fn_item = ty::type_is_bare_fn_item(t_e);
+    let t_e_is_scalar = ty::type_is_scalar(t_e);
+    let t_e_is_integral = ty::type_is_integral(t_e);
+    let t_e_is_float = ty::type_is_floating_point(t_e);
+    let t_e_is_c_enum = ty::type_is_c_like_enum(fcx.tcx(), t_e);
+
+    let t_1_is_scalar = ty::type_is_scalar(t_1);
+    let t_1_is_char = ty::type_is_char(t_1);
+    let t_1_is_bare_fn = ty::type_is_bare_fn(t_1);
+    let t_1_is_float = ty::type_is_floating_point(t_1);
+
+    // casts to scalars other than `char` and `bare fn` are trivial
+    let t_1_is_trivial = t_1_is_scalar && !t_1_is_char && !t_1_is_bare_fn;
+
+    if t_e_is_bare_fn_item && t_1_is_bare_fn {
+        demand::coerce(fcx, e.span, t_1, &e);
+    } else if t_1_is_char {
+        let t_e = fcx.infcx().shallow_resolve(t_e);
+        if t_e.sty != ty::ty_uint(ast::TyU8) {
+            fcx.type_error_message(span, |actual| {
+                format!("only `u8` can be cast as `char`, not `{}`", actual)
+            }, t_e, None);
+        }
+    } else if t_1.sty == ty::ty_bool {
+        span_err!(fcx.tcx().sess, span, E0054,
+                  "cannot cast as `bool`, compare with zero instead");
+    } else if t_1_is_float && (t_e_is_scalar || t_e_is_c_enum) && !(
+        t_e_is_integral || t_e_is_float || t_e.sty == ty::ty_bool) {
+        // Casts to float must go through an integer or boolean
+        cast_through_integer_err(fcx, span, t_1, t_e)
+    } else if t_e_is_c_enum && t_1_is_trivial {
+        if ty::type_is_unsafe_ptr(t_1) {
+            // ... and likewise with C enum -> *T
+            cast_through_integer_err(fcx, span, t_1, t_e)
+        }
+        // casts from C-like enums are allowed
+    } else if ty::type_is_region_ptr(t_e) && ty::type_is_unsafe_ptr(t_1) {
+        fn types_compatible<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, sp: Span,
+                                      t1: Ty<'tcx>, t2: Ty<'tcx>) -> bool {
+            match t1.sty {
+                ty::ty_vec(_, Some(_)) => {}
+                _ => return false
+            }
+            if ty::type_needs_infer(t2) {
+                // This prevents this special case from going off when casting
+                // to a type that isn't fully specified; e.g. `as *_`. (Issue
+                // #14893.)
+                return false
+            }
+
+            let el = ty::sequence_element_type(fcx.tcx(), t1);
+            infer::mk_eqty(fcx.infcx(),
+                           false,
+                           infer::Misc(sp),
+                           el,
+                           t2).is_ok()
+        }
+
+        // Due to the limitations of LLVM global constants,
+        // region pointers end up pointing at copies of
+        // vector elements instead of the original values.
+        // To allow unsafe pointers to work correctly, we
+        // need to special-case obtaining an unsafe pointer
+        // from a region pointer to a vector.
+
+        /* this cast is only allowed from &[T, ..n] to *T or
+        &T to *T. */
+        match (&t_e.sty, &t_1.sty) {
+            (&ty::ty_rptr(_, ty::mt { ty: mt1, mutbl: ast::MutImmutable }),
+             &ty::ty_ptr(ty::mt { ty: mt2, mutbl: ast::MutImmutable }))
+            if types_compatible(fcx, e.span, mt1, mt2) => {
+                /* this case is allowed */
+            }
+            _ => {
+                demand::coerce(fcx, e.span, t_1, &e);
+            }
+        }
+    } else if !(t_e_is_scalar && t_1_is_trivial) {
+        /*
+        If more type combinations should be supported than are
+        supported here, then file an enhancement issue and
+        record the issue number in this comment.
+        */
+        fcx.type_error_message(span, |actual| {
+            format!("non-scalar cast: `{}` as `{}`",
+                    actual,
+                    fcx.infcx().ty_to_string(t_1))
+        }, t_e, None);
+    }
+}
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 156fbfede9c..f9bf3eaf3dd 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -139,6 +139,7 @@ pub mod demand;
 pub mod method;
 mod upvar;
 pub mod wf;
+mod cast;
 mod closure;
 mod callee;
 mod compare_method;
@@ -185,7 +186,7 @@ pub struct Inherited<'a, 'tcx: 'a> {
     // back and process them.
     deferred_call_resolutions: RefCell<DefIdMap<Vec<DeferredCallResolutionHandler<'tcx>>>>,
 
-    deferred_cast_checks: RefCell<Vec<CastCheck<'tcx>>>,
+    deferred_cast_checks: RefCell<Vec<cast::CastCheck<'tcx>>>,
 }
 
 trait DeferredCallResolution<'tcx> {
@@ -194,15 +195,6 @@ trait DeferredCallResolution<'tcx> {
 
 type DeferredCallResolutionHandler<'tcx> = Box<DeferredCallResolution<'tcx>+'tcx>;
 
-/// Reifies a cast check to be checked once we have full type information for
-/// a function context.
-struct CastCheck<'tcx> {
-    expr: ast::Expr,
-    expr_ty: Ty<'tcx>,
-    cast_ty: Ty<'tcx>,
-    span: Span,
-}
-
 /// When type-checking an expression, we propagate downward
 /// whatever type hint we are able in the form of an `Expectation`.
 #[derive(Copy, Clone)]
@@ -1071,141 +1063,6 @@ fn report_cast_to_unsized_type<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
 }
 
 
-fn check_cast<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, cast: &CastCheck<'tcx>) {
-    fn cast_through_integer_err<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
-                                          span: Span,
-                                          t_1: Ty<'tcx>,
-                                          t_e: Ty<'tcx>) {
-        fcx.type_error_message(span, |actual| {
-            format!("illegal cast; cast through an \
-                    integer first: `{}` as `{}`",
-                    actual,
-                    fcx.infcx().ty_to_string(t_1))
-        }, t_e, None);
-    }
-
-    let span = cast.span;
-    let e = &cast.expr;
-    let t_e = structurally_resolved_type(fcx, span, cast.expr_ty);
-    let t_1 = structurally_resolved_type(fcx, span, cast.cast_ty);
-
-    // Check for trivial casts.
-    if !ty::type_has_ty_infer(t_1) {
-        if let Ok(()) = coercion::mk_assignty(fcx, e, t_e, t_1) {
-            if ty::type_is_numeric(t_1) && ty::type_is_numeric(t_e) {
-                fcx.tcx().sess.add_lint(lint::builtin::TRIVIAL_NUMERIC_CASTS,
-                                        e.id,
-                                        span,
-                                        format!("trivial numeric cast: `{}` as `{}`. Cast can be \
-                                                 replaced by coercion, this might require type \
-                                                 ascription or a temporary variable",
-                                                fcx.infcx().ty_to_string(t_e),
-                                                fcx.infcx().ty_to_string(t_1)));
-            } else {
-                fcx.tcx().sess.add_lint(lint::builtin::TRIVIAL_CASTS,
-                                        e.id,
-                                        span,
-                                        format!("trivial cast: `{}` as `{}`. Cast can be \
-                                                 replaced by coercion, this might require type \
-                                                 ascription or a temporary variable",
-                                                fcx.infcx().ty_to_string(t_e),
-                                                fcx.infcx().ty_to_string(t_1)));
-            }
-            return;
-        }
-    }
-
-    let t_e_is_bare_fn_item = ty::type_is_bare_fn_item(t_e);
-    let t_e_is_scalar = ty::type_is_scalar(t_e);
-    let t_e_is_integral = ty::type_is_integral(t_e);
-    let t_e_is_float = ty::type_is_floating_point(t_e);
-    let t_e_is_c_enum = ty::type_is_c_like_enum(fcx.tcx(), t_e);
-
-    let t_1_is_scalar = ty::type_is_scalar(t_1);
-    let t_1_is_char = ty::type_is_char(t_1);
-    let t_1_is_bare_fn = ty::type_is_bare_fn(t_1);
-    let t_1_is_float = ty::type_is_floating_point(t_1);
-
-    // casts to scalars other than `char` and `bare fn` are trivial
-    let t_1_is_trivial = t_1_is_scalar && !t_1_is_char && !t_1_is_bare_fn;
-
-    if t_e_is_bare_fn_item && t_1_is_bare_fn {
-        demand::coerce(fcx, e.span, t_1, &e);
-    } else if t_1_is_char {
-        let t_e = fcx.infcx().shallow_resolve(t_e);
-        if t_e.sty != ty::ty_uint(ast::TyU8) {
-            fcx.type_error_message(span, |actual| {
-                format!("only `u8` can be cast as `char`, not `{}`", actual)
-            }, t_e, None);
-        }
-    } else if t_1.sty == ty::ty_bool {
-        span_err!(fcx.tcx().sess, span, E0054,
-                  "cannot cast as `bool`, compare with zero instead");
-    } else if t_1_is_float && (t_e_is_scalar || t_e_is_c_enum) && !(
-        t_e_is_integral || t_e_is_float || t_e.sty == ty::ty_bool) {
-        // Casts to float must go through an integer or boolean
-        cast_through_integer_err(fcx, span, t_1, t_e)
-    } else if t_e_is_c_enum && t_1_is_trivial {
-        if ty::type_is_unsafe_ptr(t_1) {
-            // ... and likewise with C enum -> *T
-            cast_through_integer_err(fcx, span, t_1, t_e)
-        }
-        // casts from C-like enums are allowed
-    } else if ty::type_is_region_ptr(t_e) && ty::type_is_unsafe_ptr(t_1) {
-        fn types_compatible<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, sp: Span,
-                                      t1: Ty<'tcx>, t2: Ty<'tcx>) -> bool {
-            match t1.sty {
-                ty::ty_vec(_, Some(_)) => {}
-                _ => return false
-            }
-            if ty::type_needs_infer(t2) {
-                // This prevents this special case from going off when casting
-                // to a type that isn't fully specified; e.g. `as *_`. (Issue
-                // #14893.)
-                return false
-            }
-
-            let el = ty::sequence_element_type(fcx.tcx(), t1);
-            infer::mk_eqty(fcx.infcx(),
-                           false,
-                           infer::Misc(sp),
-                           el,
-                           t2).is_ok()
-        }
-
-        // Due to the limitations of LLVM global constants,
-        // region pointers end up pointing at copies of
-        // vector elements instead of the original values.
-        // To allow unsafe pointers to work correctly, we
-        // need to special-case obtaining an unsafe pointer
-        // from a region pointer to a vector.
-
-        /* this cast is only allowed from &[T, ..n] to *T or
-        &T to *T. */
-        match (&t_e.sty, &t_1.sty) {
-            (&ty::ty_rptr(_, ty::mt { ty: mt1, mutbl: ast::MutImmutable }),
-             &ty::ty_ptr(ty::mt { ty: mt2, mutbl: ast::MutImmutable }))
-            if types_compatible(fcx, e.span, mt1, mt2) => {
-                /* this case is allowed */
-            }
-            _ => {
-                demand::coerce(fcx, e.span, t_1, &e);
-            }
-        }
-    } else if !(t_e_is_scalar && t_1_is_trivial) {
-        /*
-        If more type combinations should be supported than are
-        supported here, then file an enhancement issue and
-        record the issue number in this comment.
-        */
-        fcx.type_error_message(span, |actual| {
-            format!("non-scalar cast: `{}` as `{}`",
-                    actual,
-                    fcx.infcx().ty_to_string(t_1))
-        }, t_e, None);
-    }
-}
-
 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
     fn tcx(&self) -> &ty::ctxt<'tcx> { self.ccx.tcx }
 
@@ -1925,7 +1782,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn check_casts(&self) {
         let mut deferred_cast_checks = self.inh.deferred_cast_checks.borrow_mut();
         for check in deferred_cast_checks.iter() {
-            check_cast(self, check);
+            cast::check_cast(self, check);
         }
 
         deferred_cast_checks.clear();
@@ -3531,12 +3388,8 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
 
             // Defer other checks until we're done type checking.
             let mut deferred_cast_checks = fcx.inh.deferred_cast_checks.borrow_mut();
-            deferred_cast_checks.push(CastCheck {
-                expr: (**e).clone(),
-                expr_ty: t_e,
-                cast_ty: t_1,
-                span: expr.span,
-            });
+            let cast_check = cast::CastCheck::new((**e).clone(), t_e, t_1, expr.span);
+            deferred_cast_checks.push(cast_check);
         }
       }
       ast::ExprVec(ref args) => {