Rollup merge of #40369 - petrochenkov:segspan, r=eddyb

Give spans to individual path segments in AST

And use these spans in path resolution diagnostics.

The spans are spans of identifiers in segments, not whole segments. I'm not sure what spans are more useful in general, but identifier spans are a better fit for resolve errors.

HIR still doesn't have spans.

Fixes https://github.com/rust-lang/rust/pull/38927#discussion_r95336667 https://github.com/rust-lang/rust/pull/38890#issuecomment-271731008

r? @nrc @eddyb

src/libsyntax/parse/parser.rs

@@ -27,7 +27,7 @@ use ast::Local;
 use ast::MacStmtStyle;
 use ast::Mac_;
 use ast::{MutTy, Mutability};
-use ast::{Pat, PatKind};
+use ast::{Pat, PatKind, PathSegment};
 use ast::{PolyTraitRef, QSelf};
 use ast::{Stmt, StmtKind};
 use ast::{VariantData, StructField};
@@ -1811,7 +1811,7 @@ impl<'a> Parser<'a> {
         };
 
         if is_global {
-            segments.insert(0, ast::PathSegment::crate_root());
+            segments.insert(0, PathSegment::crate_root());
         }
 
         // Assemble the span.
@@ -1829,11 +1829,12 @@ impl<'a> Parser<'a> {
     /// - `a::b<T,U>::c<V,W>`
     /// - `a::b<T,U>::c(V) -> W`
     /// - `a::b<T,U>::c(V)`
-    pub fn parse_path_segments_without_colons(&mut self) -> PResult<'a, Vec<ast::PathSegment>> {
+    pub fn parse_path_segments_without_colons(&mut self) -> PResult<'a, Vec<PathSegment>> {
         let mut segments = Vec::new();
         loop {
             // First, parse an identifier.
             let identifier = self.parse_path_segment_ident()?;
+            let ident_span = self.prev_span;
 
             if self.check(&token::ModSep) && self.look_ahead(1, |t| *t == token::Lt) {
                 self.bump();
@@ -1881,7 +1882,11 @@ impl<'a> Parser<'a> {
             };
 
             // Assemble and push the result.
-            segments.push(ast::PathSegment { identifier: identifier, parameters: parameters });
+            segments.push(PathSegment {
+                identifier: identifier,
+                span: ident_span,
+                parameters: parameters
+            });
 
             // Continue only if we see a `::`
             if !self.eat(&token::ModSep) {
@@ -1892,15 +1897,16 @@ impl<'a> Parser<'a> {
 
     /// Examples:
     /// - `a::b::<T,U>::c`
-    pub fn parse_path_segments_with_colons(&mut self) -> PResult<'a, Vec<ast::PathSegment>> {
+    pub fn parse_path_segments_with_colons(&mut self) -> PResult<'a, Vec<PathSegment>> {
         let mut segments = Vec::new();
         loop {
             // First, parse an identifier.
             let identifier = self.parse_path_segment_ident()?;
+            let ident_span = self.prev_span;
 
             // If we do not see a `::`, stop.
             if !self.eat(&token::ModSep) {
-                segments.push(identifier.into());
+                segments.push(PathSegment::from_ident(identifier, ident_span));
                 return Ok(segments);
             }
 
@@ -1909,8 +1915,9 @@ impl<'a> Parser<'a> {
                 // Consumed `a::b::<`, go look for types
                 let (lifetimes, types, bindings) = self.parse_generic_args()?;
                 self.expect_gt()?;
-                segments.push(ast::PathSegment {
+                segments.push(PathSegment {
                     identifier: identifier,
+                    span: ident_span,
                     parameters: ast::AngleBracketedParameterData {
                         lifetimes: lifetimes,
                         types: types,
@@ -1924,7 +1931,7 @@ impl<'a> Parser<'a> {
                 }
             } else {
                 // Consumed `a::`, go look for `b`
-                segments.push(identifier.into());
+                segments.push(PathSegment::from_ident(identifier, ident_span));
             }
         }
     }
@@ -1932,14 +1939,14 @@ impl<'a> Parser<'a> {
     /// Examples:
     /// - `a::b::c`
     pub fn parse_path_segments_without_types(&mut self)
-                                             -> PResult<'a, Vec<ast::PathSegment>> {
+                                             -> PResult<'a, Vec<PathSegment>> {
         let mut segments = Vec::new();
         loop {
             // First, parse an identifier.
             let identifier = self.parse_path_segment_ident()?;
 
             // Assemble and push the result.
-            segments.push(identifier.into());
+            segments.push(PathSegment::from_ident(identifier, self.prev_span));
 
             // If we do not see a `::` or see `::{`/`::*`, stop.
             if !self.check(&token::ModSep) || self.is_import_coupler() {
@@ -5950,7 +5957,7 @@ impl<'a> Parser<'a> {
             // `{foo, bar}`, `::{foo, bar}`, `*`, or `::*`.
             self.eat(&token::ModSep);
             let prefix = ast::Path {
-                segments: vec![ast::PathSegment::crate_root()],
+                segments: vec![PathSegment::crate_root()],
                 span: mk_sp(lo, self.span.hi),
             };
             let view_path_kind = if self.eat(&token::BinOp(token::Star)) {