[CodeComplete] Fix crash when completing ObjC block parameter with a broken type

[sammccall]

Summary

The fix isn't great, but it's hard to fix properly because the completion
code sensibly uses ParmVarDecl to represent parameters, but the AST-building
code sensibly doesn't synthesize them if the type is broken.
Also this case is apparently really rare, so it's probably not worth bending
over backwards for.

[ilya-biryukov]

LGTM

cfe/trunk/lib/Sema/SemaCodeComplete.cpp

formatBlockPlaceholder(const PrintingPolicy &Policy, const NamedDecl *BlockDecl,
                        bool SuppressBlockName = false,
                        bool SuppressBlock = false,
                        Optional<ArrayRef<QualType>> ObjCSubsts = None);
 
 static std::string
 FormatFunctionParameter(const PrintingPolicy &Policy, const ParmVarDecl *Param,
                         bool SuppressName = false, bool SuppressBlock = false,
                         Optional<ArrayRef<QualType>> ObjCSubsts = None) {
+  // Params are unavailable in FunctionTypeLoc if the FunctionType is invalid.
+  // It would be better to pass in the param Type, which is usually avaliable.
+  // But this case is rare, so just pretend we fell back to int as elsewhere.
+  if (!Param)
+    return "int";
   bool ObjCMethodParam = isa<ObjCMethodDecl>(Param->getDeclContext());
   if (Param->getType()->isDependentType() ||
       !Param->getType()->isBlockPointerType()) {
     // The argument for a dependent or non-block parameter is a placeholder
     // containing that parameter's type.
     std::string Result;
 
     if (Param->getIdentifier() && !ObjCMethodParam && !SuppressName)

cfe/trunk/test/Index/complete-blocks.m

 @interface I1
 - method7:(int (^_Nullable)(int x, int y))b;
 @end
 void f2(int (^_Nullable block)(int x, int y));
 void test_f2(I1 *o) {
   [o method7:0];
 }
 
+// Crash regression test. Param info for broken function types isn't available.
+typedef UnresolvedType *(^XXX)(float);
+@interface Foo
+-(void) foo:(XXX)arg;
+@end
+void testUnresolved(Foo* f) {
+  [f foo:0];
+}
+
 // RUN: c-index-test -code-completion-at=%s:8:1 %s | FileCheck -check-prefix=CHECK-CC1 %s
 // CHECK-CC1: FunctionDecl:{ResultType void}{TypedText f}{LeftParen (}{Placeholder ^int(int x, int y)block}{RightParen )} (50)
 // CHECK-CC1: FunctionDecl:{ResultType void}{TypedText g}{LeftParen (}{Placeholder ^(float f, double d)b}{RightParen )} (50)
 // RUN: c-index-test -code-completion-at=%s:17:6 %s | FileCheck -check-prefix=CHECK-CC2 %s
 // CHECK-CC2: ObjCInstanceMethodDecl:{ResultType id}{TypedText method2:}{Placeholder ^(float f, double d)b} (35)
 // CHECK-CC2: ObjCInstanceMethodDecl:{ResultType id}{TypedText method:}{Placeholder ^int(int x, int y)b} (35)
 // RUN: c-index-test -code-completion-at=%s:25:6 %s | FileCheck -check-prefix=CHECK-CC3 %s
 // CHECK-CC3: ObjCInstanceMethodDecl:{ResultType id}{TypedText method3:}{Placeholder ^int(void)b} (35)
 // RUN: c-index-test -code-completion-at=%s:34:6 %s | FileCheck -check-prefix=CHECK-CC4 %s
 // CHECK-CC4: ObjCInstanceMethodDecl:{ResultType id}{TypedText method4:}{Placeholder ^(void)arg} (35)
 // CHECK-CC4: ObjCInstanceMethodDecl:{ResultType id}{TypedText method5:}{Placeholder ^(void)arg5} (35)
 // RUN: c-index-test -code-completion-at=%s:25:15 %s | FileCheck -check-prefix=CHECK-CC5 %s
 // CHECK-CC5: TypedefDecl:{TypedText block_t} (50)
 // CHECK-CC5: TypedefDecl:{TypedText Class} (50)
 // CHECK-CC5-NOT: test_A
 // CHECK-CC5: {TypedText union} (50)
 
 // RUN: c-index-test -code-completion-at=%s:42:6 %s | FileCheck -check-prefix=CHECK-CC6 %s
 // CHECK-CC6: ObjCInstanceMethodDecl:{ResultType id}{TypedText method6:}{Placeholder ^(block_t block)arg} (35)
 
 // RUN: c-index-test -code-completion-at=%s:50:1 %s | FileCheck -check-prefix=CHECK-CC7 %s
 // CHECK-CC7: FunctionDecl:{ResultType void}{TypedText f2}{LeftParen (}{Placeholder ^int(int x, int y)block}{RightParen )} (50)
 // RUN: c-index-test -code-completion-at=%s:50:6 %s | FileCheck -check-prefix=CHECK-CC8 %s
 // CHECK-CC8: ObjCInstanceMethodDecl:{ResultType id}{TypedText method7:}{Placeholder ^int(int x, int y)b} (35)
+
+// RUN: c-index-test -code-completion-at=%s:59:6 %s | FileCheck -check-prefix=CHECK-CC9 %s
+// CHECK-CC9: ObjCInstanceMethodDecl:{ResultType void}{TypedText foo:}{Placeholder ^int *(int)arg} (35)