Add support for editor placeholders to Clang

This commit teaches Clang to recognize editor placeholders that are produced
when an IDE like Xcode inserts a code-completion result that includes a
placeholder. Now when the lexer sees a placeholder token, it emits an
'editor placeholder in source file' error and creates an identifier token
that represents the placeholder. The parser/sema can now recognize the
placeholders and can suppress the diagnostics related to the placeholders. This
ensures that live issues in an IDE like Xcode won't get spurious diagnostics
related to placeholders.

This commit also adds a new compiler option named '-fallow-editor-placeholders'
that silences the 'editor placeholder in source file' error. This is useful
for an IDE like Xcode as we don't want to display those errors in live issues.

rdar://31581400

Differential Revision: https://reviews.llvm.org/D32081

llvm-svn: 300667

2 files changed, 79 insertions, 5 deletions

diff --git a/clang/test/Parser/editor-placeholder-recovery.cpp b/clang/test/Parser/editor-placeholder-recovery.cpp
new file mode 100644
index 00000000000..48c290ee9a1
--- /dev/null
+++ b/clang/test/Parser/editor-placeholder-recovery.cpp
@@ -0,0 +1,71 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -fallow-editor-placeholders -DSUPPRESS -verify %s
+
+struct Struct {
+public:
+    void method(Struct &x);
+};
+
+struct <#struct name#> {
+  int <#field-name#>;
+#ifndef SUPPRESS
+  // expected-error@-3 {{editor placeholder in source file}}
+  // expected-error@-3 {{editor placeholder in source file}}
+#endif
+};
+
+typename <#typename#>::<#name#>;
+decltype(<#expression#>) foobar;
+typedef <#type#> <#name#>;
+#ifndef SUPPRESS
+  // expected-error@-4 2 {{editor placeholder in source file}}
+  // expected-error@-4 {{editor placeholder in source file}}
+  // expected-error@-4 2 {{editor placeholder in source file}}
+#endif
+
+namespace <#identifier#> {
+  <#declarations#>
+#ifndef SUPPRESS
+  // expected-error@-3 {{editor placeholder in source file}}
+  // expected-error@-3 {{editor placeholder in source file}}
+#endif
+
+}
+
+using <#qualifier#>::<#name#>;
+#ifndef SUPPRESS
+  // expected-error@-2 2 {{editor placeholder in source file}}
+#endif
+
+void avoidPlaceholderErrors(Struct &obj) {
+    static_cast< <#type#> >(<#expression#>);
+    while (<#condition#>) {
+        <#statements#>
+    }
+    obj.method(<#Struct &x#>);
+#ifndef SUPPRESS
+  // expected-error@-6 2 {{editor placeholder in source file}}
+  // expected-error@-6 {{editor placeholder in source file}}
+  // expected-error@-6 {{editor placeholder in source file}}
+  // expected-error@-5 {{editor placeholder in source file}}
+#endif
+    switch (<#expression#>) {
+        case <#constant#>:
+            <#statements#>
+#ifndef SUPPRESS
+  // expected-error@-4 {{editor placeholder in source file}}
+  // expected-error@-4 {{editor placeholder in source file}}
+  // expected-error@-4 {{editor placeholder in source file}}
+#endif
+            break;
+
+        default:
+            break;
+    }
+}
+
+void Struct::method(<#Struct &x#>, noSupressionHere) { // expected-error {{unknown type name 'noSupressionHere'}} expected-error {{C++ requires a type specifier for all declarations}}
+#ifndef SUPPRESS
+  // expected-error@-2 {{editor placeholder in source file}}
+#endif
+}
diff --git a/clang/test/Parser/placeholder-recovery.m b/clang/test/Parser/placeholder-recovery.m
index b43b0e4a57c..4f22ea770da 100644
--- a/clang/test/Parser/placeholder-recovery.m
+++ b/clang/test/Parser/placeholder-recovery.m
@@ -1,11 +1,14 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
+@protocol NSObject
+@end
+
+@protocol <#protocol name#> <NSObject> // expected-error {{editor placeholder in source file}}
+// expected-note@-1 {{protocol started here}}
+
 // FIXME: We could do much better with this, if we recognized
 // placeholders somehow. However, we're content with not generating
 // bogus 'archaic' warnings with bad location info.
-@protocol <#protocol name#> <NSObject> // expected-error {{expected identifier or '('}} \
-// expected-error 2{{expected identifier}} \
-// expected-warning{{protocol has no object type specified; defaults to qualified 'id'}}
-<#methods#>
+<#methods#> // expected-error {{editor placeholder in source file}}
 
-@end
+@end // expected-error {{prefix attribute must be followed by an interface or protocol}} expected-error {{missing '@end'}}