[CSDiagnostics] Improving inout to pointer argument conversions with optionals diagnostics

Author: LucianoPAlmeida

lib/Sema/CSDiagnostics.cpp

@@ -675,6 +675,9 @@ bool GenericArgumentsMismatchFailure::diagnoseAsError() {
       // InoutToPointer argument mismatch failure.
       if (isa<InOutExpr>(anchor)) {
         diagnostic = diag::cannot_convert_argument_value;
+        auto applyInfo = getFunctionArgApplyInfo(getLocator());
+        if (applyInfo)
+          toType = applyInfo->getParamType();
       }
       break;
     }

test/Constraints/diagnostics.swift

@@ -1443,3 +1443,30 @@ func assignGenericMismatch() {
   // expected-note@-3 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}
   // expected-note@-4 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
 }
+
+// [Int] to [String]? argument to param conversion
+let value: [Int] = []
+func gericArgToParamOptional(_ param: [String]?) {}
+
+gericArgToParamOptional(value) // expected-error {{convert value of type '[Int]' to expected argument type '[String]?'}}
+// expected-note@-1 {{arguments to generic parameter 'Element' ('Int' and 'String') are expected to be equal}}
+
+// Inout Expr conversions
+func gericArgToParamInout1(_ x: inout [[Int]]) {}
+func gericArgToParamInout2(_ x: inout [[String]]) {
+  gericArgToParamInout1(&x) // expected-error {{cannot convert value of type '[[String]]' to expected argument type '[[Int]]'}}
+  // expected-note@-1 {{arguments to generic parameter 'Element' ('String' and 'Int') are expected to be equal}}
+}
+
+func gericArgToParamInoutOptional(_ x: inout [[String]]?) {
+  gericArgToParamInout1(&x) // expected-error {{cannot convert value of type '[[String]]?' to expected argument type '[[Int]]'}}
+  // expected-note@-1 {{arguments to generic parameter 'Element' ('String' and 'Int') are expected to be equal}}
+  // expected-error@-2 {{value of optional type '[[String]]?' must be unwrapped to a value of type '[[String]]'}}
+  // expected-note@-3 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
+}
+
+func gericArgToParamInout(_ x: inout [[Int]]) { // expected-note {{change variable type to '[[String]]?' if it doesn't need to be declared as '[[Int]]'}}
+  gericArgToParamInoutOptional(&x) // expected-error {{cannot convert value of type '[[Int]]' to expected argument type '[[String]]?'}}
+  // expected-note@-1 {{arguments to generic parameter 'Element' ('Int' and 'String') are expected to be equal}}
+  // expected-error@-2 {{inout argument could be set to a value with a type other than '[[Int]]'; use a value declared as type '[[String]]?' instead}}
+}

test/Constraints/valid_pointer_conversions.swift

@@ -31,13 +31,13 @@ func givesPtr(_ str: String) {
   takesDoubleOptionalPtr(i) // expected-error {{cannot convert value of type 'Int' to expected argument type 'UnsafeRawPointer??'}}
   takesMutableDoubleOptionalPtr(arr) // expected-error {{cannot convert value of type '[Int]' to expected argument type 'UnsafeMutableRawPointer??'}}
 
-  takesMutableDoubleOptionalTypedPtr(&i) // expected-error {{cannot convert value of type 'UnsafeMutablePointer<Int>' to expected argument type 'UnsafeMutablePointer<Double>'}}
+  takesMutableDoubleOptionalTypedPtr(&i) // expected-error {{cannot convert value of type 'UnsafeMutablePointer<Int>' to expected argument type 'UnsafeMutablePointer<Double>??'}}
   // expected-note@-1 {{arguments to generic parameter 'Pointee' ('Int' and 'Double') are expected to be equal}}
 }
 
 // SR12382
 func SR12382(_ x: UnsafeMutablePointer<Double>??) {}
 
 var i = 0
-SR12382(&i) // expected-error {{cannot convert value of type 'UnsafeMutablePointer<Int>' to expected argument type 'UnsafeMutablePointer<Double>'}}
+SR12382(&i) // expected-error {{cannot convert value of type 'UnsafeMutablePointer<Int>' to expected argument type 'UnsafeMutablePointer<Double>??'}}
 // expected-note@-1 {{arguments to generic parameter 'Pointee' ('Int' and 'Double') are expected to be equal}}