12 files changed, 48 insertions, 69 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 0ea8f6a63..153458644 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -25,7 +25,7 @@ mod parser;
 pub mod syntax_kinds;
 pub use text::{TextRange, TextUnit};
 pub use tree::{File, Node, SyntaxKind, Token};
-pub(crate) use tree::{FileBuilder, Sink};
+pub(crate) use tree::{ErrorMsg, FileBuilder, Sink};
 pub use lexer::{next_token, tokenize};
 pub use parser::parse;
 
diff --git a/src/parser/event.rs b/src/parser/event.rs
index e97350c89..90348398e 100644
--- a/src/parser/event.rs
+++ b/src/parser/event.rs
@@ -1,4 +1,4 @@
-use {File, FileBuilder, Sink, SyntaxKind, TextUnit, Token};
+use {ErrorMsg, File, FileBuilder, Sink, SyntaxKind, TextUnit, Token};
 use syntax_kinds::TOMBSTONE;
 use super::is_insignificant;
 
@@ -140,7 +140,9 @@ pub(super) fn to_file(text: String, tokens: &[Token], events: Vec<Event>) -> Fil
                 }
                 builder.leaf(kind, len);
             }
-            &Event::Error { ref message } => builder.error().message(message.clone()).emit(),
+            &Event::Error { ref message } => builder.error(ErrorMsg {
+                message: message.clone(),
+            }),
         }
     }
     builder.finish()
diff --git a/src/parser/grammar/attributes.rs b/src/parser/grammar/attributes.rs
index 8bf04afce..92dfb99ef 100644
--- a/src/parser/grammar/attributes.rs
+++ b/src/parser/grammar/attributes.rs
@@ -37,7 +37,7 @@ fn meta_item(p: &mut Parser) {
             EQ => {
                 p.bump();
                 if !expressions::literal(p) {
-                    p.error().message("expected literal").emit();
+                    p.error("expected literal");
                 }
             }
             L_PAREN => meta_item_arg_list(p),
@@ -45,7 +45,7 @@ fn meta_item(p: &mut Parser) {
         }
         meta_item.complete(p, META_ITEM);
     } else {
-        p.error().message("expected attribute value").emit()
+        p.error("expected attribute value");
     }
 }
 
@@ -60,12 +60,12 @@ fn meta_item_arg_list(p: &mut Parser) {
                 let message = "expected attribute";
 
                 if items::ITEM_FIRST.contains(c) {
-                    p.error().message(message).emit();
+                    p.error(message);
                     return;
                 }
 
                 let err = p.start();
-                p.error().message(message).emit();
+                p.error(message);
                 p.bump();
                 err.complete(p, ERROR);
                 continue;
diff --git a/src/parser/grammar/expressions.rs b/src/parser/grammar/expressions.rs
index 8caaf3553..3704cb16f 100644
--- a/src/parser/grammar/expressions.rs
+++ b/src/parser/grammar/expressions.rs
@@ -15,6 +15,6 @@ pub(super) fn literal(p: &mut Parser) -> bool {
 
 pub(super) fn expr(p: &mut Parser) {
     if !literal(p) {
-        p.error().message("expected expression").emit();
+        p.error("expected expression");
     }
 }
diff --git a/src/parser/grammar/items/mod.rs b/src/parser/grammar/items/mod.rs
index 37f2ab132..b73628ec0 100644
--- a/src/parser/grammar/items/mod.rs
+++ b/src/parser/grammar/items/mod.rs
@@ -51,7 +51,7 @@ fn item(p: &mut Parser) {
                 // extern struct Foo;
                 _ => {
                     item.abandon(p);
-                    p.error().message("expected `fn` or `{`").emit();
+                    p.error("expected `fn` or `{`");
                     return;
                 }
             }
@@ -121,7 +121,7 @@ fn item(p: &mut Parser) {
                     abi(p);
                     if !p.at(FN_KW) {
                         item.abandon(p);
-                        p.error().message("expected function").emit();
+                        p.error("expected function");
                         return;
                     }
                     fn_item(p);
@@ -144,7 +144,7 @@ fn item(p: &mut Parser) {
                     if t == L_CURLY {
                         error_block(p, message);
                     } else {
-                        p.error().message(message).emit();
+                        p.error(message);
                     }
                     return;
                 }
@@ -234,7 +234,7 @@ fn fn_item(p: &mut Parser) {
     if p.at(L_PAREN) {
         fn_value_parameters(p);
     } else {
-        p.error().message("expected function arguments").emit();
+        p.error("expected function arguments");
     }
 
     if p.at(L_CURLY) {
diff --git a/src/parser/grammar/items/structs.rs b/src/parser/grammar/items/structs.rs
index 69d95c698..640b940e4 100644
--- a/src/parser/grammar/items/structs.rs
+++ b/src/parser/grammar/items/structs.rs
@@ -19,7 +19,7 @@ pub(super) fn struct_item(p: &mut Parser) {
                 L_CURLY => named_fields(p),
                 _ => {
                     //TODO: special case `(` error message
-                    p.error().message("expected `;` or `{`").emit();
+                    p.error("expected `;` or `{`");
                     return;
                 }
             }
@@ -34,7 +34,7 @@ pub(super) fn struct_item(p: &mut Parser) {
             p.expect(SEMI);
         }
         _ => {
-            p.error().message("expected `;`, `{`, or `(`").emit();
+            p.error("expected `;`, `{`, or `(`");
             return;
         }
     }
diff --git a/src/parser/grammar/items/use_item.rs b/src/parser/grammar/items/use_item.rs
index 38e7b3f8a..a3f7f0da8 100644
--- a/src/parser/grammar/items/use_item.rs
+++ b/src/parser/grammar/items/use_item.rs
@@ -37,7 +37,7 @@ fn use_tree(p: &mut Parser) {
                         L_CURLY => nested_trees(p),
                         _ => {
                             // is this unreachable?
-                            p.error().message("expected `{` or `*`").emit();
+                            p.error("expected `{` or `*`");
                         }
                     }
                 }
diff --git a/src/parser/grammar/mod.rs b/src/parser/grammar/mod.rs
index afce308d0..b949583ff 100644
--- a/src/parser/grammar/mod.rs
+++ b/src/parser/grammar/mod.rs
@@ -53,7 +53,7 @@ fn alias(p: &mut Parser) -> bool {
 fn error_block(p: &mut Parser, message: &str) {
     assert!(p.at(L_CURLY));
     let err = p.start();
-    p.error().message(message).emit();
+    p.error(message);
     p.bump();
     let mut level: u32 = 1;
     while level > 0 && !p.at(EOF) {
@@ -74,7 +74,7 @@ impl<'p> Parser<'p> {
 
     fn err_and_bump(&mut self, message: &str) {
         let err = self.start();
-        self.error().message(message).emit();
+        self.error(message);
         self.bump();
         err.complete(self, ERROR);
     }
@@ -84,7 +84,7 @@ impl<'p> Parser<'p> {
             self.bump();
             true
         } else {
-            self.error().message(format!("expected {:?}", kind)).emit();
+            self.error(format!("expected {:?}", kind));
             false
         }
     }
diff --git a/src/parser/grammar/paths.rs b/src/parser/grammar/paths.rs
index 6efac2610..a7fc90774 100644
--- a/src/parser/grammar/paths.rs
+++ b/src/parser/grammar/paths.rs
@@ -43,7 +43,9 @@ fn path_segment(p: &mut Parser, first: bool) {
     }
     match p.current() {
         IDENT | SELF_KW | SUPER_KW => p.bump(),
-        _ => p.error().message("expected identifier").emit(),
+        _ => {
+            p.error("expected identifier");
+        }
     };
     segment.complete(p, PATH_SEGMENT);
 }
diff --git a/src/parser/parser.rs b/src/parser/parser.rs
index 752d532d0..7c8e47cb6 100644
--- a/src/parser/parser.rs
+++ b/src/parser/parser.rs
@@ -129,8 +129,8 @@ impl<'t> Parser<'t> {
         m
     }
 
-    pub(crate) fn error<'p>(&'p mut self) -> ErrorBuilder<'p, 't> {
-        ErrorBuilder::new(self)
+    pub(crate) fn error<'p, T: Into<String>>(&'p mut self, msg: T) -> ErrorBuilder<'p, 't> {
+        ErrorBuilder::new(self, msg.into())
     }
 
     pub(crate) fn bump(&mut self) {
@@ -175,25 +175,19 @@ impl<'t> Parser<'t> {
 }
 
 pub(crate) struct ErrorBuilder<'p, 't: 'p> {
-    message: Option<String>,
+    message: String,
     parser: &'p mut Parser<'t>,
 }
 
-impl<'t, 'p> ErrorBuilder<'p, 't> {
-    fn new(parser: &'p mut Parser<'t>) -> Self {
-        ErrorBuilder {
-            message: None,
-            parser,
-        }
-    }
-
-    pub fn message<M: Into<String>>(mut self, m: M) -> Self {
-        self.message = Some(m.into());
-        self
+impl<'p, 't: 'p> Drop for ErrorBuilder<'p, 't> {
+    fn drop(&mut self) {
+        let message = ::std::mem::replace(&mut self.message, String::new());
+        self.parser.event(Event::Error { message });
     }
+}
 
-    pub fn emit(self) {
-        let message = self.message.expect("Error message not set");
-        self.parser.event(Event::Error { message });
+impl<'t, 'p> ErrorBuilder<'p, 't> {
+    fn new(parser: &'p mut Parser<'t>, message: String) -> Self {
+        ErrorBuilder { message, parser }
     }
 }
diff --git a/src/tree/file_builder.rs b/src/tree/file_builder.rs
index 47038496d..3c7e2d7cf 100644
--- a/src/tree/file_builder.rs
+++ b/src/tree/file_builder.rs
@@ -14,7 +14,7 @@ pub(crate) trait Sink {
     fn leaf(&mut self, kind: SyntaxKind, len: TextUnit);
     fn start_internal(&mut self, kind: SyntaxKind);
     fn finish_internal(&mut self);
-    fn error(&mut self) -> ErrorBuilder;
+    fn error(&mut self, err: ErrorMsg);
 }
 
 #[derive(Debug)]
@@ -22,7 +22,8 @@ pub(crate) struct FileBuilder {
     text: String,
     nodes: Vec<NodeData>,
     errors: Vec<SyntaxErrorData>,
-    in_progress: Vec<(NodeIdx, Option<NodeIdx>)>, // (parent, last_child)
+    in_progress: Vec<(NodeIdx, Option<NodeIdx>)>,
+    // (parent, last_child)
     pos: TextUnit,
 }
 
@@ -65,8 +66,13 @@ impl Sink for FileBuilder {
         }
     }
 
-    fn error(&mut self) -> ErrorBuilder {
-        ErrorBuilder::new(self)
+    fn error(&mut self, err: ErrorMsg) {
+        let &(node, after_child) = self.in_progress.last().unwrap();
+        self.errors.push(SyntaxErrorData {
+            node,
+            message: err.message,
+            after_child,
+        })
     }
 }
 
@@ -149,32 +155,7 @@ fn grow(left: &mut TextRange, right: TextRange) {
     *left = TextRange::from_to(left.start(), right.end())
 }
 
-#[derive(Debug)]
-pub struct ErrorBuilder<'f> {
-    message: Option<String>,
-    builder: &'f mut FileBuilder,
-}
-
-impl<'f> ErrorBuilder<'f> {
-    fn new(builder: &'f mut FileBuilder) -> Self {
-        ErrorBuilder {
-            message: None,
-            builder,
-        }
-    }
-
-    pub fn message<M: Into<String>>(mut self, m: M) -> Self {
-        self.message = Some(m.into());
-        self
-    }
-
-    pub fn emit(self) {
-        let message = self.message.expect("Error message not set");
-        let &(node, after_child) = self.builder.in_progress.last().unwrap();
-        self.builder.errors.push(SyntaxErrorData {
-            node,
-            message,
-            after_child,
-        })
-    }
+#[derive(Default)]
+pub(crate) struct ErrorMsg {
+    pub(crate) message: String,
 }
diff --git a/src/tree/mod.rs b/src/tree/mod.rs
index 9ed0504c7..ebf26777b 100644
--- a/src/tree/mod.rs
+++ b/src/tree/mod.rs
@@ -4,7 +4,7 @@ use std::fmt;
 use std::cmp;
 
 mod file_builder;
-pub(crate) use self::file_builder::{FileBuilder, Sink};
+pub(crate) use self::file_builder::{ErrorMsg, FileBuilder, Sink};
 
 pub use syntax_kinds::SyntaxKind;