[SR-13239] Adjust error message to split inferrence source into notes

Author: LucianoPAlmeida

include/swift/AST/DiagnosticsSema.def

@@ -380,10 +380,12 @@ ERROR(cannot_convert_argument_value_generic,none,
 ERROR(conflicting_arguments_for_generic_parameter,none,
       "conflicting arguments to generic parameter %0 (%1)",
       (Type, StringRef))
-ERROR(conflicting_inferred_generic_parameter_result_and_closure,none,
-      "conflicting inferred types from call result and closure "
-      "argument to generic parameter %0 (%1)",
-      (Type, StringRef))
+NOTE(generic_parameter_inferred_from_closure,none,
+     "generic parameter %0 inferred as %1 from closure return expression",
+     (Type, Type))
+NOTE(generic_parameter_inferred_from_result_context,none,
+     "generic parameter %0 inferred as %1 from context",
+     (Type, Type))
 
 // @_nonEphemeral conversion diagnostics
 ERROR(cannot_pass_type_to_non_ephemeral,none,

lib/Sema/ConstraintSystem.cpp

@@ -3787,7 +3787,7 @@ static bool diagnoseContextualFunctionCallGenericAmbiguity(
     return cs.typeVarOccursInType(typeVar, paramFnType->getResult());
   };
 
-  llvm::SmallVector<ClosureExpr *, 4> closureArguments;
+  llvm::SmallVector<ClosureExpr *, 2> closureArguments;
   // A single closure argument.
   if (auto *closure =
           getAsExpr<ClosureExpr>(AE->getArg()->getSemanticsProvidingExpr())) {
@@ -3837,7 +3837,7 @@ static bool diagnoseContextualFunctionCallGenericAmbiguity(
         return true;
       })) {
 
-    if (genericParamInferredTypes.size() <= 1)
+    if (genericParamInferredTypes.size() != 2)
       return false;
 
     auto &DE = cs.getASTContext().Diags;
@@ -3848,9 +3848,16 @@ static bool diagnoseContextualFunctionCallGenericAmbiguity(
         [&](Type argType) { OS << "'" << argType << "'"; },
         [&OS] { OS << " vs. "; });
 
-    DE.diagnose(AE->getLoc(),
-                diag::conflicting_inferred_generic_parameter_result_and_closure,
+    DE.diagnose(AE->getLoc(), diag::conflicting_arguments_for_generic_parameter,
                 GP, OS.str());
+
+    DE.diagnose(AE->getLoc(),
+                diag::generic_parameter_inferred_from_result_context, GP,
+                genericParamInferredTypes.back());
+    DE.diagnose(closureArguments.front()->getStartLoc(),
+                diag::generic_parameter_inferred_from_closure, GP,
+                genericParamInferredTypes.front());
+
     return true;
   }
   return false;

test/expr/closure/closures.swift

@@ -633,29 +633,33 @@ func callitVariadic<T>(_ fs: () -> T...) -> T {
 }
 
 func testSR13239_Tuple() -> Int {
-  // expected-error@+1{{conflicting inferred types from call result and closure argument to generic parameter 'T' ('()' vs. 'Int')}}
-  callitTuple(1) {
+  // expected-error@+2{{conflicting arguments to generic parameter 'T' ('()' vs. 'Int')}}
+  // expected-note@+1:3{{generic parameter 'T' inferred as 'Int' from context}}
+  callitTuple(1) { // expected-note@:18{{generic parameter 'T' inferred as '()' from closure return expression}}
     (print("hello"), 0) 
   }
 }
 
 func testSR13239() -> Int {
-  // expected-error@+1{{conflicting inferred types from call result and closure argument to generic parameter 'T' ('()' vs. 'Int')}}
-  callit {
+  // expected-error@+2{{conflicting arguments to generic parameter 'T' ('()' vs. 'Int')}}
+  // expected-note@+1:3{{generic parameter 'T' inferred as 'Int' from context}}
+  callit { // expected-note@:10{{generic parameter 'T' inferred as '()' from closure return expression}}
     print("hello")
   }
 }
 
 func testSR13239_Args() -> Int {
-  // expected-error@+1{{conflicting inferred types from call result and closure argument to generic parameter 'T' ('()' vs. 'Int')}}
-  callitArgs(1) {
+  // expected-error@+2{{conflicting arguments to generic parameter 'T' ('()' vs. 'Int')}}
+  // expected-note@+1:3{{generic parameter 'T' inferred as 'Int' from context}}
+  callitArgs(1) { // expected-note@:17{{generic parameter 'T' inferred as '()' from closure return expression}}
     print("hello") 
   }
 }
 
 func testSR13239_ArgsFn() -> Int {
-  // expected-error@+1{{conflicting inferred types from call result and closure argument to generic parameter 'T' ('()' vs. 'Int')}}
-  callitArgsFn(1) {
+  // expected-error@+2{{conflicting arguments to generic parameter 'T' ('()' vs. 'Int')}}
+  // expected-note@+1:3{{generic parameter 'T' inferred as 'Int' from context}}
+  callitArgsFn(1) { // expected-note@:19{{generic parameter 'T' inferred as '()' from closure return expression}}
     { print("hello") } 
   }
 }
@@ -675,8 +679,9 @@ func testSR13239_GenericArg() -> Int {
 }
 
 func testSR13239_Variadic() -> Int {
-  // expected-error@+1{{conflicting inferred types from call result and closure argument to generic parameter 'T' ('()' vs. 'Int')}}
-  callitVariadic({
+  // expected-error@+2{{conflicting arguments to generic parameter 'T' ('()' vs. 'Int')}}
+  // expected-note@+1:3{{generic parameter 'T' inferred as 'Int' from context}}
+  callitVariadic({ // expected-note@:18{{generic parameter 'T' inferred as '()' from closure return expression}}
     print("hello")
   })
 }