EmbeddedSwiftDiagnostics: improve error message for non-specialized generic function calls

Tell the user if the specialization isn't done because of a dynamic Self type.

rdar://150865684

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/ModulePasses/EmbeddedSwiftDiagnostics.swift

@@ -189,6 +189,11 @@ private struct FunctionChecker {
       case let wmi as WitnessMethodInst:
         throw Diagnostic(.embedded_cannot_specialize_witness_method, wmi.member, at: apply.location)
       default:
+        if apply.substitutionMap.replacementTypes.contains(where: { $0.hasDynamicSelf }),
+           apply.calleeHasGenericSelfMetatypeParameter
+        {
+          throw Diagnostic(.embedded_call_generic_function_with_dynamic_self, at: apply.location)
+        }
         throw Diagnostic(.embedded_call_generic_function, at: apply.location)
       }
     }
@@ -368,6 +373,15 @@ private extension ApplySite {
     }
     return false
   }
+
+  var calleeHasGenericSelfMetatypeParameter: Bool {
+    let convention = FunctionConvention(for: callee.type.canonicalType, in: parentFunction)
+    guard convention.hasSelfParameter, let selfParam = convention.parameters.last else {
+      return false
+    }
+    let selfParamType = selfParam.type
+    return selfParamType.isMetatype && selfParamType.instanceTypeOfMetatype.isGenericTypeParameter
+  }
 }
 
 private extension Type {

include/swift/AST/DiagnosticsSIL.def

@@ -415,7 +415,9 @@ ERROR(embedded_swift_allocating,none,
 ERROR(embedded_capture_of_generic_value_with_deinit,none,
       "capturing generic non-copyable type with deinit in escaping closure not supported in embedded Swift", ())
 ERROR(embedded_call_generic_function,none,
-      "cannot specialize generic function in this context", ())
+      "cannot specialize generic function or default protocol method in this context", ())
+ERROR(embedded_call_generic_function_with_dynamic_self,none,
+      "cannot call an initializer or static method, which is defined as default protocol method, from a class method or initializer", ())
 NOTE(embedded_specialization_called_from,none,
       "generic specialization called here", ())
 NOTE(embedded_existential_created,none,

test/embedded/generic-error.swift

@@ -0,0 +1,25 @@
+// RUN: %target-swift-emit-ir -parse-as-library -module-name main -verify %s -enable-experimental-feature Embedded -swift-version 5 -wmo -o /dev/null
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: optimized_stdlib
+// REQUIRES: swift_feature_Embedded
+
+// We don't support calling a default witness method (which is generic) with dynamic self.
+
+public protocol P {
+  init(x: Int)
+}
+
+extension P {
+  init(y: Int) {
+    self.init(x: y)
+  }
+}
+
+public class C: P {
+  public required init(x: Int) {}
+
+  public convenience init(z: Int) {
+    self.init(y: z)  // expected-error {{cannot call an initializer or static method, which is defined as default protocol method, from a class method or initializer}}
+  }
+}