Fix <rdar://problem/22108559> QoI: Confusing error message when calli…

…ng an instance method as a class method

lib/Sema/CSDiag.cpp

@@ -1700,11 +1700,7 @@ bool CalleeCandidateInfo::diagnoseAnyStructuralArgumentError(Expr *fnExpr,
   // here.
   if (size() != 1) return false;
 
-  // We only handle structural errors here.
-  if (closeness != CC_ArgumentLabelMismatch &&
-      closeness != CC_ArgumentCountMismatch)
-    return false;
-
+
   auto args = decomposeArgParamType(argExpr->getType());
   auto params = decomposeArgParamType(candidates[0].getArgumentType());
 
@@ -1731,6 +1727,11 @@ bool CalleeCandidateInfo::diagnoseAnyStructuralArgumentError(Expr *fnExpr,
       }
   }
 
+  // We only handle structural errors here.
+  if (closeness != CC_ArgumentLabelMismatch &&
+      closeness != CC_ArgumentCountMismatch)
+    return false;
+
   SmallVector<Identifier, 4> correctNames;
   unsigned OOOArgIdx = ~0U, OOOPrevArgIdx = ~0U;
   unsigned extraArgIdx = ~0U, missingParamIdx = ~0U;
@@ -3266,6 +3267,15 @@ typeCheckArgumentChildIndependently(Expr *argExpr, Type argType,
     if (candidates.size() == 1 && !argType)
       argType = candidates[0].getArgumentType();
   }
+
+  // If our candidates are instance members at curry level #0, then the argument
+  // being provided is the receiver type for the instance.  We produce better
+  // diagnostics when we don't force the self type down.
+  if (argType && !candidates.empty() &&
+      candidates[0].decl->isInstanceMember() && candidates[0].level == 0 &&
+      !isa<SubscriptDecl>(candidates[0].decl))
+    argType = Type();
+
 
   // FIXME: This should all just be a matter of getting type type of the
   // sub-expression, but this doesn't work well when typeCheckChildIndependently

test/Constraints/diagnostics.swift

@@ -339,7 +339,7 @@ c.method2(1.0)(b: 2.0) // expected-error {{cannot convert value of type 'Double'
 CurriedClass.method1(c)()
 _ = CurriedClass.method1(c)
 CurriedClass.method1(c)(1)         // expected-error {{argument passed to call that takes no arguments}}
-CurriedClass.method1(2.0)(1)       // expected-error {{cannot convert value of type 'Double' to expected argument type 'CurriedClass'}}
+CurriedClass.method1(2.0)(1)       // expected-error {{use of instance member 'method1' on type 'CurriedClass'; did you mean to use a value of type 'CurriedClass' instead?}}
 
 CurriedClass.method2(c)(32)(b: 1)
 _ = CurriedClass.method2(c)
@@ -380,7 +380,7 @@ CurriedClass.m1(2, b: 42)   // expected-error {{use of instance member 'm1' on t
 
 
 // <rdar://problem/22108559> QoI: Confusing error message when calling an instance method as a class method
-CurriedClass.m2(12)  // expected-error {{cannot convert value of type 'Int' to expected argument type 'CurriedClass'}}
+CurriedClass.m2(12)  // expected-error {{use of instance member 'm2' on type 'CurriedClass'; did you mean to use a value of type 'CurriedClass' instead?}}