Rollup merge of #63528 - petrochenkov:anyany, r=estebank

syntax: Remove `DummyResult::expr_only`

The effect is that if a built-in macro both returns an erroneous AST fragment and is used in unexpected position, then the incorrect position error won't be reported.

This combination of two errors should be rare and isn't worth an extra field that makes people ask questions in comments.
(There wasn't even a test making sure it worked.)

Addresses https://github.com/rust-lang/rust/pull/63468#discussion_r313504644
r? @estebank

1 files changed, 6 insertions, 33 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 7f4feff6be6..11544d43ac3 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -405,7 +405,6 @@ impl MacResult for MacEager {
 /// after hitting errors.
 #[derive(Copy, Clone)]
 pub struct DummyResult {
-    expr_only: bool,
     is_error: bool,
     span: Span,
 }
@@ -416,21 +415,12 @@ impl DummyResult {
     /// Use this as a return value after hitting any errors and
     /// calling `span_err`.
     pub fn any(span: Span) -> Box<dyn MacResult+'static> {
-        Box::new(DummyResult { expr_only: false, is_error: true, span })
+        Box::new(DummyResult { is_error: true, span })
     }
 
     /// Same as `any`, but must be a valid fragment, not error.
     pub fn any_valid(span: Span) -> Box<dyn MacResult+'static> {
-        Box::new(DummyResult { expr_only: false, is_error: false, span })
-    }
-
-    /// Creates a default MacResult that can only be an expression.
-    ///
-    /// Use this for macros that must expand to an expression, so even
-    /// if an error is encountered internally, the user will receive
-    /// an error that they also used it in the wrong place.
-    pub fn expr(span: Span) -> Box<dyn MacResult+'static> {
-        Box::new(DummyResult { expr_only: true, is_error: true, span })
+        Box::new(DummyResult { is_error: false, span })
     }
 
     /// A plain dummy expression.
@@ -472,36 +462,19 @@ impl MacResult for DummyResult {
     }
 
     fn make_items(self: Box<DummyResult>) -> Option<SmallVec<[P<ast::Item>; 1]>> {
-        // this code needs a comment... why not always just return the Some() ?
-        if self.expr_only {
-            None
-        } else {
-            Some(SmallVec::new())
-        }
+        Some(SmallVec::new())
     }
 
     fn make_impl_items(self: Box<DummyResult>) -> Option<SmallVec<[ast::ImplItem; 1]>> {
-        if self.expr_only {
-            None
-        } else {
-            Some(SmallVec::new())
-        }
+        Some(SmallVec::new())
     }
 
     fn make_trait_items(self: Box<DummyResult>) -> Option<SmallVec<[ast::TraitItem; 1]>> {
-        if self.expr_only {
-            None
-        } else {
-            Some(SmallVec::new())
-        }
+        Some(SmallVec::new())
     }
 
     fn make_foreign_items(self: Box<Self>) -> Option<SmallVec<[ast::ForeignItem; 1]>> {
-        if self.expr_only {
-            None
-        } else {
-            Some(SmallVec::new())
-        }
+        Some(SmallVec::new())
     }
 
     fn make_stmts(self: Box<DummyResult>) -> Option<SmallVec<[ast::Stmt; 1]>> {