[CSDiagnostics] Add MissingCall failure

It's used to diagnose cases when function/method are used as
a property instead of being called.

Author: xedin

lib/Sema/CSDiag.cpp

@@ -7392,26 +7392,9 @@ bool FailureDiagnosis::diagnoseMemberFailures(
   // Produce a specific diagnostic + fixit for this situation.
   if (auto baseFTy = baseObjTy->getAs<AnyFunctionType>()) {
     if (baseExpr && baseFTy->getParams().empty()) {
-      SourceLoc insertLoc = baseExpr->getEndLoc();
-
-      if (auto *DRE = dyn_cast<DeclRefExpr>(baseExpr)) {
-        diagnose(baseExpr->getLoc(), diag::did_not_call_function,
-                 DRE->getDecl()->getBaseName().getIdentifier())
-            .fixItInsertAfter(insertLoc, "()");
-        return true;
-      }
-
-      if (auto *DSCE = dyn_cast<DotSyntaxCallExpr>(baseExpr))
-        if (auto *DRE = dyn_cast<DeclRefExpr>(DSCE->getFn())) {
-          diagnose(baseExpr->getLoc(), diag::did_not_call_method,
-                   DRE->getDecl()->getBaseName().getIdentifier())
-              .fixItInsertAfter(insertLoc, "()");
-          return true;
-        }
-
-      diagnose(baseExpr->getLoc(), diag::did_not_call_function_value)
-          .fixItInsertAfter(insertLoc, "()");
-      return true;
+      auto failure =
+          MissingCallFailure(expr, CS, CS.getConstraintLocator(baseExpr));
+      return failure.diagnoseAsError();
     }
   }
 

lib/Sema/CSDiagnostics.cpp

@@ -1240,3 +1240,38 @@ bool NonOptionalUnwrapFailure::diagnoseAsError() {
 
   return true;
 }
+
+bool MissingCallFailure::diagnoseAsError() {
+  auto *baseExpr = getAnchor();
+  SourceLoc insertLoc = baseExpr->getEndLoc();
+
+  if (auto *FVE = dyn_cast<ForceValueExpr>(baseExpr))
+    baseExpr = FVE->getSubExpr();
+
+  if (auto *DRE = dyn_cast<DeclRefExpr>(baseExpr)) {
+    emitDiagnostic(baseExpr->getLoc(), diag::did_not_call_function,
+                   DRE->getDecl()->getBaseName().getIdentifier())
+        .fixItInsertAfter(insertLoc, "()");
+    return true;
+  }
+
+  if (auto *UDE = dyn_cast<UnresolvedDotExpr>(baseExpr)) {
+    emitDiagnostic(baseExpr->getLoc(), diag::did_not_call_method,
+                   UDE->getName().getBaseIdentifier())
+        .fixItInsertAfter(insertLoc, "()");
+    return true;
+  }
+
+  if (auto *DSCE = dyn_cast<DotSyntaxCallExpr>(baseExpr)) {
+    if (auto *DRE = dyn_cast<DeclRefExpr>(DSCE->getFn())) {
+      emitDiagnostic(baseExpr->getLoc(), diag::did_not_call_method,
+                     DRE->getDecl()->getBaseName().getIdentifier())
+          .fixItInsertAfter(insertLoc, "()");
+      return true;
+    }
+  }
+
+  emitDiagnostic(baseExpr->getLoc(), diag::did_not_call_function_value)
+      .fixItInsertAfter(insertLoc, "()");
+  return true;
+}

lib/Sema/CSDiagnostics.h

@@ -630,6 +630,15 @@ class NonOptionalUnwrapFailure final : public FailureDiagnostic {
   bool diagnoseAsError() override;
 };
 
+class MissingCallFailure final : public FailureDiagnostic {
+public:
+  MissingCallFailure(Expr *root, ConstraintSystem &cs,
+                     ConstraintLocator *locator)
+      : FailureDiagnostic(root, cs, locator) {}
+
+  bool diagnoseAsError() override;
+};
+
 } // end namespace constraints
 } // end namespace swift
 

lib/Sema/CSFix.cpp

@@ -227,7 +227,8 @@ RemoveUnwrap *RemoveUnwrap::create(ConstraintSystem &cs, Type baseType,
 }
 
 bool InsertExplicitCall::diagnose(Expr *root, bool asNote) const {
-  return false;
+  auto failure = MissingCallFailure(root, getConstraintSystem(), getLocator());
+  return failure.diagnose(asNote);
 }
 
 InsertExplicitCall *InsertExplicitCall::create(ConstraintSystem &cs,

test/Constraints/fixes.swift

@@ -104,9 +104,10 @@ class U {
 
 class T {
     func m1() {
-        // FIXME: should apply nullary function fixit here. {{function produces expected type 'U'; did you mean to call it with '()'?}}
-        // <rdar://problem/17741575>
-        let l = self.m2!.prop1 // expected-error{{cannot force unwrap value of non-optional type '() -> U?'}} {{24-25=}}
+      // <rdar://problem/17741575>
+      let l = self.m2!.prop1
+      // expected-error@-1 {{cannot force unwrap value of non-optional type '() -> U?'}} {{22-23=}}
+      // expected-error@-2 {{method 'm2' was used as a property; add () to call it}}  {{23-23=()}}
     }
 
     func m2() -> U! {