syntax: Treat error literals in more principled way

5 files changed, 14 insertions, 12 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 598232f9f8f..02fbcb14fa5 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1368,7 +1368,7 @@ pub enum LitKind {
     FloatUnsuffixed(Symbol),
     /// A boolean literal.
     Bool(bool),
-    /// A recovered character literal that contains mutliple `char`s, most likely a typo.
+    /// Placeholder for a literal that wasn't well-formed in some way.
     Err(Symbol),
 }
 
@@ -1406,10 +1406,10 @@ impl LitKind {
             | LitKind::ByteStr(..)
             | LitKind::Byte(..)
             | LitKind::Char(..)
-            | LitKind::Err(..)
             | LitKind::Int(_, LitIntType::Unsuffixed)
             | LitKind::FloatUnsuffixed(..)
-            | LitKind::Bool(..) => true,
+            | LitKind::Bool(..)
+            | LitKind::Err(..) => true,
             // suffixed variants
             LitKind::Int(_, LitIntType::Signed(..))
             | LitKind::Int(_, LitIntType::Unsigned(..))
diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs
index d2a614c4a54..2889f8edfc6 100644
--- a/src/libsyntax/mut_visit.rs
+++ b/src/libsyntax/mut_visit.rs
@@ -1101,7 +1101,6 @@ pub fn noop_visit_expr<T: MutVisitor>(Expr { node, id, span, attrs }: &mut Expr,
             vis.visit_expr(rhs);
         }
         ExprKind::Unary(_unop, ohs) => vis.visit_expr(ohs),
-        ExprKind::Lit(_lit) => {}
         ExprKind::Cast(expr, ty) => {
             vis.visit_expr(expr);
             vis.visit_ty(ty);
@@ -1225,7 +1224,7 @@ pub fn noop_visit_expr<T: MutVisitor>(Expr { node, id, span, attrs }: &mut Expr,
         }
         ExprKind::Try(expr) => vis.visit_expr(expr),
         ExprKind::TryBlock(body) => vis.visit_block(body),
-        ExprKind::Err => {}
+        ExprKind::Lit(_) | ExprKind::Err => {}
     }
     vis.visit_id(id);
     vis.visit_span(span);
diff --git a/src/libsyntax/parse/literal.rs b/src/libsyntax/parse/literal.rs
index 7d5356ffe4d..467ad6ccfbe 100644
--- a/src/libsyntax/parse/literal.rs
+++ b/src/libsyntax/parse/literal.rs
@@ -311,7 +311,11 @@ impl<'a> Parser<'a> {
                 let (lit, span) = (token.expect_lit(), token.span);
                 self.bump();
                 err.report(&self.sess.span_diagnostic, lit, span);
-                let lit = token::Lit::new(token::Err, lit.symbol, lit.suffix);
+                // Pack possible quotes and prefixes from the original literal into
+                // the error literal's symbol so they can be pretty-printed faithfully.
+                let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
+                let symbol = Symbol::intern(&pprust::literal_to_string(suffixless_lit));
+                let lit = token::Lit::new(token::Err, symbol, lit.suffix);
                 Lit::from_lit_token(lit, span).map_err(|_| unreachable!())
             }
         }
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 07acfb5dc86..d922e1896cc 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -168,9 +168,6 @@ pub fn literal_to_string(lit: token::Lit) -> String {
     let mut out = match kind {
         token::Byte          => format!("b'{}'", symbol),
         token::Char          => format!("'{}'", symbol),
-        token::Bool          |
-        token::Float         |
-        token::Integer       => symbol.to_string(),
         token::Str           => format!("\"{}\"", symbol),
         token::StrRaw(n)     => format!("r{delim}\"{string}\"{delim}",
                                         delim="#".repeat(n as usize),
@@ -179,7 +176,10 @@ pub fn literal_to_string(lit: token::Lit) -> String {
         token::ByteStrRaw(n) => format!("br{delim}\"{string}\"{delim}",
                                         delim="#".repeat(n as usize),
                                         string=symbol),
-        token::Err           => format!("'{}'", symbol),
+        token::Integer       |
+        token::Float         |
+        token::Bool          |
+        token::Err           => symbol.to_string(),
     };
 
     if let Some(suffix) = suffix {
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 4e6a8274a47..24b0c372471 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -714,7 +714,6 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
         ExprKind::AddrOf(_, ref subexpression) | ExprKind::Unary(_, ref subexpression) => {
             visitor.visit_expr(subexpression)
         }
-        ExprKind::Lit(_) => {}
         ExprKind::Cast(ref subexpression, ref typ) | ExprKind::Type(ref subexpression, ref typ) => {
             visitor.visit_expr(subexpression);
             visitor.visit_ty(typ)
@@ -826,7 +825,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
         ExprKind::TryBlock(ref body) => {
             visitor.visit_block(body)
         }
-        ExprKind::Err => {}
+        ExprKind::Lit(_) | ExprKind::Err => {}
     }
 
     visitor.visit_expr_post(expression)