Implement a new identifier-classification scheme where Sema

performs name lookup for an identifier and resolves it to a
type/expression/template/etc. in the same step. This scheme is
intended to improve both performance (by reducing the number of
redundant name lookups for a given identifier token) and error
recovery (by giving Sema a chance to correct type names before the
parser has decided that the identifier isn't a type name). For
example, this allows us to properly typo-correct type names at the
beginning of a statement:

t.c:6:3: error: use of undeclared identifier 'integer'; did you mean
'Integer'?
  integer *i = 0;
  ^~~~~~~
  Integer
t.c:1:13: note: 'Integer' declared here
typedef int Integer;
            ^


Previously, we wouldn't give a Fix-It because the typo correction
occurred after the parser had checked whether "integer" was a type
name (via Sema::getTypeName(), which isn't allowed to typo-correct)
and therefore decided to parse "integer * i = 0" as an expression. By
typo-correcting earlier, we typo-correct to the type name Integer and
parse this as a declaration. 

Moreover, in this context, we can also typo-correct identifiers to
keywords, e.g.,

t.c:7:3: error: use of undeclared identifier 'vid'; did you mean
'void'?
  vid *p = i;
  ^~~
  void

and recover appropriately.

Note that this is very much a work-in-progress. The new
Sema::ClassifyName is only used for expression-or-declaration
disambiguation in C at the statement level. The next steps will be to
make this work for the same disambiguation in C++ (where
functional-style casts make some trouble), then push it
further into the parser to eliminate more redundant name lookups.

Fixes <rdar://problem/7963833> for C and starts us down the path of
<rdar://problem/8172000>.

llvm-svn: 130082

1 files changed, 12 insertions, 0 deletions

diff --git a/clang/test/FixIt/typo.c b/clang/test/FixIt/typo.c
index 01ff3a09cf3..8a277c75f03 100644
--- a/clang/test/FixIt/typo.c
+++ b/clang/test/FixIt/typo.c
@@ -2,6 +2,7 @@
 // RUN: cp %s %t
 // RUN: %clang_cc1 -fsyntax-only -fixit -x c %t || true
 // RUN: %clang_cc1 -fsyntax-only -pedantic -Werror -x c %t
+// RUN: grep "Rectangle" %t
 struct Point {
   float x, y;
 };
@@ -23,3 +24,14 @@ struct Window window = {
   topleft.x = 3.14, // expected-error{{field designator 'topleft' does not refer to any field in type 'struct Rectangle'; did you mean 'top_left'?}}
   2.71818, 5.0, 6.0, Red
 };
+
+void test() {
+  Rectangle r1; // expected-error{{must use 'struct' tag to refer to type 'Rectangle'}}
+  r1.top_left.x = 0;
+
+  typedef struct Rectangle Rectangle; // expected-note{{'Rectangle' declared here}}
+  rectangle *r2 = &r1; // expected-error{{use of undeclared identifier 'rectangle'; did you mean 'Rectangle'?}}
+  r2->top_left.y = 0;
+  unsinged *ptr = 0; // expected-error{{use of undeclared identifier 'unsinged'; did you mean 'unsigned'?}}
+  *ptr = 17;
+}