Add unexisting_power_operator diagnostic when using unexisting ** operator in swift

Author: mininny

include/swift/AST/DiagnosticsSema.def

@@ -844,6 +844,9 @@ NOTE(unspaced_binary_operators_candidate,none,
 ERROR(unspaced_unary_operator,none,
       "unary operators must not be juxtaposed; parenthesize inner expression",
       ())
+ERROR(nonexistent_power_operator,none,
+      "no operator '**' is defined; did you mean 'pow(_:_:)'?",
+      ())
 
 ERROR(cannot_find_in_scope,none,
       "cannot %select{find|find operator}1 %0 in scope", (DeclNameRef, bool))

lib/Sema/PreCheckExpr.cpp

@@ -238,6 +238,30 @@ static bool diagnoseRangeOperatorMisspell(DiagnosticEngine &Diags,
   return false;
 }
 
+static bool diagnoseNonexistentPowerOperator(DiagnosticEngine &Diags,
+                                             UnresolvedDeclRefExpr *UDRE,
+                                             DeclContext *DC) {
+  auto name = UDRE->getName().getBaseIdentifier();
+  if (!(name.isOperator() && name.is("**")))
+    return false;
+
+  DC = DC->getModuleScopeContext();
+
+  auto &ctx = DC->getASTContext();
+  DeclNameRef powerName(ctx.getIdentifier("pow"));
+
+  // Look if 'pow(_:_:)' exists within current context.
+  auto lookUp = TypeChecker::lookupUnqualified(
+      DC, powerName, UDRE->getLoc(), defaultUnqualifiedLookupOptions);
+  if (lookUp) {
+    Diags.diagnose(UDRE->getLoc(), diag::nonexistent_power_operator)
+        .highlight(UDRE->getSourceRange());
+    return true;
+  }
+
+  return false;
+}
+
 static bool diagnoseIncDecOperator(DiagnosticEngine &Diags,
                                    UnresolvedDeclRefExpr *UDRE) {
   auto name = UDRE->getName().getBaseIdentifier();
@@ -427,7 +451,8 @@ Expr *TypeChecker::resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE,
     // e.g. (x*-4) that needs whitespace.
     if (diagnoseRangeOperatorMisspell(Context.Diags, UDRE) ||
         diagnoseIncDecOperator(Context.Diags, UDRE) ||
-        diagnoseOperatorJuxtaposition(UDRE, DC)) {
+        diagnoseOperatorJuxtaposition(UDRE, DC) ||
+        diagnoseNonexistentPowerOperator(Context.Diags, UDRE, DC)) {
       return errorResult();
     }
 

test/decl/func/operator.swift

@@ -422,3 +422,11 @@ func testPostfixOperatorOnTuple<A, B>(a: A, b: B) {
   (§)((a, (b, b), a))
   _ = (a, ((), (b, (a, a), b)§), a)§
 }
+
+func testNonexistentPowerOperatorWithPowFunctionOutOfScope() {
+  func a(_ value: Double) { }
+  let x: Double = 3.0
+  let y: Double = 3.0
+  let z: Double = x**y // expected-error {{cannot find operator '**' in scope}}
+  let w: Double = a(x**2.0) // expected-error {{cannot find operator '**' in scope}}
+}

test/decl/operator/declared_power_operator.swift

@@ -0,0 +1,18 @@
+// RUN: %target-typecheck-verify-swift
+
+infix operator **
+
+func **(a: Double, b: Double) -> Double { return 0 }
+
+func testDeclaredPowerOperator() { 
+  let x: Double = 3.0
+  let y: Double = 3.0
+  _ = 2.0**2.0 // no error
+  _ = x**y // no error
+}
+
+func testDeclaredPowerOperatorWithIncompatibleType() { 
+  let x: Int8 = 3
+  let y: Int8 = 3
+  _ = x**y // expected-error{{cannot convert value of type 'Int8' to expected argument type 'Double'}} expected-error{{cannot convert value of type 'Int8' to expected argument type 'Double'}}
+}

test/decl/operator/power_operator_imported.swift

@@ -0,0 +1,11 @@
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -I %S/Inputs/custom-modules -I %t %s -verify
+
+import cfuncs
+
+func testNonexistentPowerOperatorWithPowFunctionInScope() {
+  func a(_ value: Double) { }
+  let x: Double = 3.0
+  let y: Double = 3.0
+  let z: Double = x**y // expected-error {{no operator '**' is defined; did you mean 'pow(_:_:)'?}}
+  let w: Double = a(x**2.0) // expected-error {{no operator '**' is defined; did you mean 'pow(_:_:)'?}}
+}