Improve 0-argument -Wvexing-parse diagnostic by adding notes with fix-its:

 - If the declarator is at the start of a line, and the previous line contained
   another declarator and ended with a comma, then that comma was probably a
   typo for a semicolon:

   int n = 0, m = 1, l = 2, // k = 5;
   myImportantFunctionCall(); // oops!

 - If removing the parentheses would correctly initialize the object, then
   produce a note suggesting that fix.

 - Otherwise, if there is a simple initializer we can suggest which performs
   value-initialization, then provide a note suggesting a correction to that
   initializer.

Sema::Declarator now tracks the location of the comma prior to the declarator in
the declaration, if there is one, to facilitate providing the note. The code to
determine an appropriate initializer from the -Wuninitialized warning has been
factored out to allow use in both that and -Wvexing-parse.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148072 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 80 insertions, 0 deletions

diff --git a/test/FixIt/fixit-vexing-parse.cpp b/test/FixIt/fixit-vexing-parse.cpp
new file mode 100644
index 0000000000..0f0505f983
--- /dev/null
+++ b/test/FixIt/fixit-vexing-parse.cpp
@@ -0,0 +1,80 @@
+// RUN: %clang_cc1 -verify -x c++ %s
+// RUN: %clang_cc1 -fdiagnostics-parseable-fixits -x c++ %s 2>&1 | FileCheck %s
+
+struct S {
+  int n;
+};
+
+struct T {
+  T();
+  int n;
+};
+
+struct U {
+  ~U();
+  int n;
+};
+
+struct V {
+  ~V();
+};
+
+struct W : V {
+};
+
+struct X : U {
+};
+
+int F1();
+S F2();
+
+namespace N {
+  void test() {
+    // CHECK: fix-it:"{{.*}}":{34:9-34:11}:" = {}"
+    S s1(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+
+    // CHECK: fix-it:"{{.*}}":{38:9-38:10}:";"
+    // CHECK: fix-it:"{{.*}}":{39:7-39:9}:" = {}"
+    S s2, // expected-note {{change this ',' to a ';' to call 'F2'}}
+    F2(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+
+    // CHECK: fix-it:"{{.*}}":{43:9-43:11}:""
+    // CHECK: fix-it:"{{.*}}":{44:9-44:11}:""
+    T t1(), // expected-warning {{function declaration}} expected-note {{remove parentheses}}
+      t2(); // expected-warning {{function declaration}} expected-note {{remove parentheses}}
+
+    // CHECK: fix-it:"{{.*}}":{47:8-47:10}:" = {}"
+    U u(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+
+    // CHECK: fix-it:"{{.*}}":{50:8-50:10}:""
+    V v(); // expected-warning {{function declaration}} expected-note {{remove parentheses}}
+
+    // CHECK: fix-it:"{{.*}}":{53:8-53:10}:""
+    W w(); // expected-warning {{function declaration}} expected-note {{remove parentheses}}
+
+    // TODO: Removing the parens here would not initialize U::n.
+    // Maybe suggest an " = X()" initializer for this case?
+    // Maybe suggest removing the parens anyway?
+    X x(); // expected-warning {{function declaration}}
+
+    // CHECK: fix-it:"{{.*}}":{61:11-61:13}:" = 0"
+    int n1(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+
+    // CHECK: fix-it:"{{.*}}":{65:11-65:12}:";"
+    // CHECK: fix-it:"{{.*}}":{66:7-66:9}:" = 0"
+    int n2, // expected-note {{change this ',' to a ';' to call 'F1'}}
+    F1(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+
+    // CHECK: fix-it:"{{.*}}":{69:13-69:15}:" = 0.0"
+    double d(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+
+    typedef void *Ptr;
+
+    // CHECK: fix-it:"{{.*}}":{74:10-74:12}:" = 0"
+    Ptr p(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+
+#define NULL 0
+    // CHECK: fix-it:"{{.*}}":{78:10-78:12}:" = NULL"
+    Ptr p(); // expected-warning {{function declaration}} expected-note {{replace parentheses with an initializer}}
+  }
+}