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

Move E0379 check from typeck to ast validation

Part of rust-lang#35233.
Extension of rust-lang#35338, rust-lang#35364.
Fixes rust-lang#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))

src/libsyntax/feature_gate.rs

@@ -30,7 +30,7 @@ use ast::{NodeId, PatKind};
 use ast;
 use attr;
 use attr::AttrMetaMethods;
-use codemap::CodeMap;
+use codemap::{CodeMap, Spanned};
 use syntax_pos::Span;
 use errors::Handler;
 use visit::{self, FnKind, Visitor};
@@ -1046,7 +1046,7 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
                 _node_id: NodeId) {
         // check for const fn declarations
         match fn_kind {
-            FnKind::ItemFn(_, _, _, ast::Constness::Const, _, _) => {
+            FnKind::ItemFn(_, _, _, Spanned { node: ast::Constness::Const, .. }, _, _) => {
                 gate_feature_post!(&self, const_fn, span, "const fn is unstable");
             }
             _ => {
@@ -1078,7 +1078,7 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
                 if block.is_none() {
                     self.check_abi(sig.abi, ti.span);
                 }
-                if sig.constness == ast::Constness::Const {
+                if sig.constness.node == ast::Constness::Const {
                     gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
                 }
             }
@@ -1105,7 +1105,7 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
                                   "associated constants are experimental")
             }
             ast::ImplItemKind::Method(ref sig, _) => {
-                if sig.constness == ast::Constness::Const {
+                if sig.constness.node == ast::Constness::Const {
                     gate_feature_post!(&self, const_fn, ii.span, "const fn is unstable");
                 }
             }

src/libsyntax/parse/mod.rs

@@ -937,7 +937,10 @@ mod tests {
                                 variadic: false
                             }),
                                     ast::Unsafety::Normal,
-                                    ast::Constness::NotConst,
+                                    Spanned {
+                                        span: sp(0,2),
+                                        node: ast::Constness::NotConst,
+                                    },
                                     Abi::Rust,
                                     ast::Generics{ // no idea on either of these:
                                         lifetimes: Vec::new(),

src/libsyntax/parse/parser.rs

@@ -39,7 +39,7 @@ use ast::{ViewPath, ViewPathGlob, ViewPathList, ViewPathSimple};
 use ast::{Visibility, WhereClause};
 use ast::{BinOpKind, UnOp};
 use ast;
-use codemap::{self, CodeMap, Spanned, spanned};
+use codemap::{self, CodeMap, Spanned, spanned, respan};
 use syntax_pos::{self, Span, BytePos, mk_sp};
 use errors::{self, DiagnosticBuilder};
 use ext::tt::macro_parser;
@@ -4770,7 +4770,7 @@ impl<'a> Parser<'a> {
     /// Parse an item-position function declaration.
     fn parse_item_fn(&mut self,
                      unsafety: Unsafety,
-                     constness: Constness,
+                     constness: Spanned<Constness>,
                      abi: abi::Abi)
                      -> PResult<'a, ItemInfo> {
         let (ident, mut generics) = self.parse_fn_header()?;
@@ -4796,18 +4796,21 @@ impl<'a> Parser<'a> {
     /// - `extern fn`
     /// - etc
     pub fn parse_fn_front_matter(&mut self)
-                                 -> PResult<'a, (ast::Constness, ast::Unsafety, abi::Abi)> {
+                                 -> PResult<'a, (Spanned<ast::Constness>,
+                                                ast::Unsafety,
+                                                abi::Abi)> {
         let is_const_fn = self.eat_keyword(keywords::Const);
+        let const_span = self.last_span;
         let unsafety = self.parse_unsafety()?;
         let (constness, unsafety, abi) = if is_const_fn {
-            (Constness::Const, unsafety, Abi::Rust)
+            (respan(const_span, Constness::Const), unsafety, Abi::Rust)
         } else {
             let abi = if self.eat_keyword(keywords::Extern) {
                 self.parse_opt_abi()?.unwrap_or(Abi::C)
             } else {
                 Abi::Rust
             };
-            (Constness::NotConst, unsafety, abi)
+            (respan(self.last_span, Constness::NotConst), unsafety, abi)
         };
         self.expect_keyword(keywords::Fn)?;
         Ok((constness, unsafety, abi))
@@ -5706,9 +5709,12 @@ impl<'a> Parser<'a> {
 
             if self.eat_keyword(keywords::Fn) {
                 // EXTERN FUNCTION ITEM
+                let fn_span = self.last_span;
                 let abi = opt_abi.unwrap_or(Abi::C);
                 let (ident, item_, extra_attrs) =
-                    self.parse_item_fn(Unsafety::Normal, Constness::NotConst, abi)?;
+                    self.parse_item_fn(Unsafety::Normal,
+                                       respan(fn_span, Constness::NotConst),
+                                       abi)?;
                 let last_span = self.last_span;
                 let item = self.mk_item(lo,
                                         last_span.hi,
@@ -5742,6 +5748,7 @@ impl<'a> Parser<'a> {
             return Ok(Some(item));
         }
         if self.eat_keyword(keywords::Const) {
+            let const_span = self.last_span;
             if self.check_keyword(keywords::Fn)
                 || (self.check_keyword(keywords::Unsafe)
                     && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
@@ -5753,7 +5760,9 @@ impl<'a> Parser<'a> {
                 };
                 self.bump();
                 let (ident, item_, extra_attrs) =
-                    self.parse_item_fn(unsafety, Constness::Const, Abi::Rust)?;
+                    self.parse_item_fn(unsafety,
+                                       respan(const_span, Constness::Const),
+                                       Abi::Rust)?;
                 let last_span = self.last_span;
                 let item = self.mk_item(lo,
                                         last_span.hi,
@@ -5817,8 +5826,11 @@ impl<'a> Parser<'a> {
         if self.check_keyword(keywords::Fn) {
             // FUNCTION ITEM
             self.bump();
+            let fn_span = self.last_span;
             let (ident, item_, extra_attrs) =
-                self.parse_item_fn(Unsafety::Normal, Constness::NotConst, Abi::Rust)?;
+                self.parse_item_fn(Unsafety::Normal,
+                                   respan(fn_span, Constness::NotConst),
+                                   Abi::Rust)?;
             let last_span = self.last_span;
             let item = self.mk_item(lo,
                                     last_span.hi,
@@ -5838,8 +5850,11 @@ impl<'a> Parser<'a> {
                 Abi::Rust
             };
             self.expect_keyword(keywords::Fn)?;
+            let fn_span = self.last_span;
             let (ident, item_, extra_attrs) =
-                self.parse_item_fn(Unsafety::Unsafe, Constness::NotConst, abi)?;
+                self.parse_item_fn(Unsafety::Unsafe,
+                                   respan(fn_span, Constness::NotConst),
+                                   abi)?;
             let last_span = self.last_span;
             let item = self.mk_item(lo,
                                     last_span.hi,

src/libsyntax/print/pprust.rs

@@ -1185,7 +1185,7 @@ impl<'a> State<'a> {
                 try!(self.print_fn(
                     decl,
                     unsafety,
-                    constness,
+                    constness.node,
                     abi,
                     Some(item.ident),
                     typarams,
@@ -1519,7 +1519,7 @@ impl<'a> State<'a> {
                             -> io::Result<()> {
         self.print_fn(&m.decl,
                       m.unsafety,
-                      m.constness,
+                      m.constness.node,
                       m.abi,
                       Some(ident),
                       &m.generics,

src/libsyntax/test.rs

@@ -24,7 +24,7 @@ use attr;
 use syntax_pos::{self, DUMMY_SP, NO_EXPANSION, Span, FileMap, BytePos};
 use std::rc::Rc;
 
-use codemap::{self, CodeMap, ExpnInfo, NameAndSpan, MacroAttribute};
+use codemap::{self, CodeMap, ExpnInfo, NameAndSpan, MacroAttribute, dummy_spanned};
 use errors;
 use errors::snippet::{SnippetData};
 use config;
@@ -485,7 +485,7 @@ fn mk_main(cx: &mut TestCtxt) -> P<ast::Item> {
     let main_body = ecx.block(sp, vec![call_test_main]);
     let main = ast::ItemKind::Fn(ecx.fn_decl(vec![], main_ret_ty),
                            ast::Unsafety::Normal,
-                           ast::Constness::NotConst,
+                           dummy_spanned(ast::Constness::NotConst),
                            ::abi::Abi::Rust, ast::Generics::default(), main_body);
     let main = P(ast::Item {
         ident: token::str_to_ident("main"),