Rollup merge of #35480 - KiChjang:e0379-bonus, r=nikomatsakis

Move E0379 check from typeck to ast validation

Part of #35233.
Extension of #35338, #35364.
Fixes #35404.

Author: jseyfried

src/librustc/hir/lowering.rs

@@ -804,8 +804,8 @@ impl<'a> LoweringContext<'a> {
         }
     }
 
-    fn lower_constness(&mut self, c: Constness) -> hir::Constness {
-        match c {
+    fn lower_constness(&mut self, c: Spanned<Constness>) -> hir::Constness {
+        match c.node {
             Constness::Const => hir::Constness::Const,
             Constness::NotConst => hir::Constness::NotConst,
         }

src/librustc/hir/map/blocks.rs

@@ -23,13 +23,13 @@
 
 pub use self::Code::*;
 
+use hir as ast;
 use hir::map::{self, Node};
-use syntax::abi;
 use hir::{Block, FnDecl};
+use hir::intravisit::FnKind;
+use syntax::abi;
 use syntax::ast::{Attribute, Name, NodeId};
-use hir as ast;
 use syntax_pos::Span;
-use hir::intravisit::FnKind;
 
 /// An FnLikeNode is a Node that is like a fn, in that it has a decl
 /// and a body (as well as a NodeId, a span, etc).

src/librustc/infer/error_reporting.rs

@@ -1030,7 +1030,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                     = node_inner.expect("expect item fn");
         let rebuilder = Rebuilder::new(self.tcx, fn_decl, generics, same_regions, &life_giver);
         let (fn_decl, generics) = rebuilder.rebuild();
-        self.give_expl_lifetime_param(err, &fn_decl, unsafety, constness, name, &generics, span);
+        self.give_expl_lifetime_param(
+            err, &fn_decl, unsafety, constness, name, &generics, span);
     }
 
     pub fn issue_32330_warnings(&self, span: Span, issue32330s: &[ty::Issue32330]) {

src/librustc_passes/ast_validation.rs

@@ -20,6 +20,7 @@ use rustc::lint;
 use rustc::session::Session;
 use syntax::ast::*;
 use syntax::attr;
+use syntax::codemap::Spanned;
 use syntax::parse::token::{self, keywords};
 use syntax::visit::{self, Visitor};
 use syntax_pos::Span;
@@ -69,6 +70,18 @@ impl<'a> AstValidator<'a> {
             }
         }
     }
+
+    fn check_trait_fn_not_const(&self, constness: Spanned<Constness>) {
+        match constness.node {
+            Constness::Const => {
+                struct_span_err!(self.session, constness.span, E0379,
+                                 "trait fns cannot be declared const")
+                    .span_label(constness.span, &format!("trait fns cannot be const"))
+                    .emit();
+            }
+            _ => {}
+        }
+    }
 }
 
 impl<'a> Visitor for AstValidator<'a> {
@@ -146,6 +159,9 @@ impl<'a> Visitor for AstValidator<'a> {
                 self.invalid_visibility(&item.vis, item.span, None);
                 for impl_item in impl_items {
                     self.invalid_visibility(&impl_item.vis, impl_item.span, None);
+                    if let ImplItemKind::Method(ref sig, _) = impl_item.node {
+                        self.check_trait_fn_not_const(sig.constness);
+                    }
                 }
             }
             ItemKind::Impl(_, _, _, None, _, _) => {
@@ -169,6 +185,13 @@ impl<'a> Visitor for AstValidator<'a> {
                     }
                 }
             }
+            ItemKind::Trait(_, _, _, ref trait_items) => {
+                for trait_item in trait_items {
+                    if let TraitItemKind::Method(ref sig, _) = trait_item.node {
+                        self.check_trait_fn_not_const(sig.constness);
+                    }
+                }
+            }
             ItemKind::Mod(_) => {
                 // Ensure that `path` attributes on modules are recorded as used (c.f. #35584).
                 attr::first_attr_value_str_by_name(&item.attrs, "path");

src/librustc_passes/consts.rs

@@ -147,7 +147,8 @@ impl<'a, 'gcx> CheckCrateVisitor<'a, 'gcx> {
         }
 
         let mode = match fk {
-            FnKind::ItemFn(_, _, _, hir::Constness::Const, _, _, _) => Mode::ConstFn,
+            FnKind::ItemFn(_, _, _, hir::Constness::Const, _, _, _)
+                => Mode::ConstFn,
             FnKind::Method(_, m, _, _) => {
                 if m.constness == hir::Constness::Const {
                     Mode::ConstFn

src/librustc_passes/diagnostics.rs

@@ -176,6 +176,13 @@ fn some_func() {
 ```
 "##,
 
+E0379: r##"
+Trait methods cannot be declared `const` by design. For more information, see
+[RFC 911].
+
+[RFC 911]: https://github.com/rust-lang/rfcs/pull/911
+"##,
+
 E0449: r##"
 A visibility qualifier was used when it was unnecessary. Erroneous code
 examples:

src/librustc_typeck/check/mod.rs

@@ -836,13 +836,9 @@ pub fn check_item_body<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>, it: &'tcx hir::Item) {
                     check_const(ccx, &expr, trait_item.id)
                 }
                 hir::MethodTraitItem(ref sig, Some(ref body)) => {
-                    check_trait_fn_not_const(ccx, trait_item.span, sig.constness);
-
                     check_bare_fn(ccx, &sig.decl, body, trait_item.id);
                 }
-                hir::MethodTraitItem(ref sig, None) => {
-                    check_trait_fn_not_const(ccx, trait_item.span, sig.constness);
-                }
+                hir::MethodTraitItem(_, None) |
                 hir::ConstTraitItem(_, None) |
                 hir::TypeTraitItem(..) => {
                     // Nothing to do.
@@ -854,22 +850,6 @@ pub fn check_item_body<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>, it: &'tcx hir::Item) {
     }
 }
 
-fn check_trait_fn_not_const<'a,'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
-                                     span: Span,
-                                     constness: hir::Constness)
-{
-    match constness {
-        hir::Constness::NotConst => {
-            // good
-        }
-        hir::Constness::Const => {
-            struct_span_err!(ccx.tcx.sess, span, E0379, "trait fns cannot be declared const")
-                .span_label(span, &format!("trait fns cannot be const"))
-                .emit()
-        }
-    }
-}
-
 fn check_on_unimplemented<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
                                     def_id: DefId,
                                     item: &hir::Item) {
@@ -1027,9 +1007,7 @@ fn check_impl_items_against_trait<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
                          err.emit()
                     }
                 }
-                hir::ImplItemKind::Method(ref sig, ref body) => {
-                    check_trait_fn_not_const(ccx, impl_item.span, sig.constness);
-
+                hir::ImplItemKind::Method(_, ref body) => {
                     let impl_method = match ty_impl_item {
                         ty::MethodTraitItem(ref mti) => mti,
                         _ => span_bug!(impl_item.span, "non-method impl-item for method")

src/librustc_typeck/diagnostics.rs

@@ -3422,13 +3422,6 @@ containing the unsized type is the last and only unsized type field in the
 struct.
 "##,
 
-E0379: r##"
-Trait methods cannot be declared `const` by design. For more information, see
-[RFC 911].
-
-[RFC 911]: https://github.com/rust-lang/rfcs/pull/911
-"##,
-
 E0380: r##"
 Default impls are only allowed for traits with no methods or associated items.
 For more information see the [opt-in builtin traits RFC](https://github.com/rust

src/libsyntax/ast.rs

@@ -1122,7 +1122,7 @@ pub struct MutTy {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct MethodSig {
     pub unsafety: Unsafety,
-    pub constness: Constness,
+    pub constness: Spanned<Constness>,
     pub abi: Abi,
     pub decl: P<FnDecl>,
     pub generics: Generics,
@@ -1820,7 +1820,7 @@ pub enum ItemKind {
     /// A function declaration (`fn` or `pub fn`).
     ///
     /// E.g. `fn foo(bar: usize) -> usize { .. }`
-    Fn(P<FnDecl>, Unsafety, Constness, Abi, Generics, P<Block>),
+    Fn(P<FnDecl>, Unsafety, Spanned<Constness>, Abi, Generics, P<Block>),
     /// A module declaration (`mod` or `pub mod`).
     ///
     /// E.g. `mod foo;` or `mod foo { .. }`

src/libsyntax/ext/build.rs

@@ -12,7 +12,7 @@ use abi::Abi;
 use ast::{self, Ident, Generics, Expr, BlockCheckMode, UnOp, PatKind};
 use attr;
 use syntax_pos::{Span, DUMMY_SP, Pos};
-use codemap::{respan, Spanned};
+use codemap::{dummy_spanned, respan, Spanned};
 use ext::base::ExtCtxt;
 use parse::token::{self, keywords, InternedString};
 use ptr::P;
@@ -1016,7 +1016,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
                   Vec::new(),
                   ast::ItemKind::Fn(self.fn_decl(inputs, output),
                               ast::Unsafety::Normal,
-                              ast::Constness::NotConst,
+                              dummy_spanned(ast::Constness::NotConst),
                               Abi::Rust,
                               generics,
                               body))