Merge pull request #60008 from xymus/implicit-import-conformances

[Sema] Report exported uses of conformances that are implicitly imported

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -2919,7 +2919,8 @@ ERROR(conformance_from_implementation_only_module,none,
       "in an extension with conditional conformances}2; "
       "%select{%3 has been imported as implementation-only|"
       "the conformance is declared as SPI in %3|"
-      "the conformance is declared as SPI}4",
+      "the conformance is declared as SPI|"
+      "%3 was not imported by this file}4",
       (Type, Identifier, unsigned, Identifier, unsigned))
 NOTE(assoc_conformance_from_implementation_only_module,none,
      "in associated type %0 (inferred as %1)", (Type, Type))

test/Sema/implicit-import-in-inlinable-code.swift

@@ -25,13 +25,19 @@ public struct ImportedType {
     public init() {}
 }
 
+// Test exportability of conformance uses
+public protocol SomeProtocol {}
+public func conformanceUse(_ a: SomeProtocol) {}
+
 // BEGIN libB.swift
 import libA
 
 extension ImportedType {
     public func implicitlyImportedMethod() {}
 }
 
+extension ImportedType : SomeProtocol {}
+
 /// Client module
 // BEGIN clientFileA-Swift5.swift
 import libA
@@ -42,6 +48,8 @@ import libA
 
   // Expected implicit imports are still fine
   a.localModuleMethod()
+
+  conformanceUse(a) // expected-warning {{cannot use conformance of 'ImportedType' to 'SomeProtocol' here; 'libB' was not imported by this file; this is an error in Swift 6}}
 }
 
 // BEGIN clientFileA-OldCheck.swift
@@ -54,6 +62,8 @@ import libA
 
   // Expected implicit imports are still fine
   a.localModuleMethod()
+
+  conformanceUse(a) // expected-warning {{cannot use conformance of 'ImportedType' to 'SomeProtocol' here; 'libB' was not imported by this file; this is an error in Swift 6}}
 }
 
 // BEGIN clientFileA-Swift6.swift
@@ -65,6 +75,8 @@ import libA
 
   // Expected implicit imports are still fine
   a.localModuleMethod()
+
+  conformanceUse(a) // expected-error {{cannot use conformance of 'ImportedType' to 'SomeProtocol' here; 'libB' was not imported by this file}}
 }
 
 // BEGIN clientFileB.swift