[Sema] Consistently run MiscDiagnostics on macro arguments

Previously we would only run MiscDiagnostics
passes on macro arguments for some statement
diagnostics, update the expression walkers that
inherit from BaseDiagnosticWalker such that we
consistently do MiscDiagnostics on macro arguments.

Author: hamishknight

lib/Sema/MiscDiagnostics.h

@@ -139,9 +139,9 @@ namespace swift {
     }
 
     MacroWalking getMacroWalkingBehavior() const override {
-      // Macro expansions will be walked when they're type-checked, not as
-      // part of the surrounding code.
-      return MacroWalking::None;
+      // We only want to walk macro arguments. Expansions will be walked when
+      // they're type-checked, not as part of the surrounding code.
+      return MacroWalking::Arguments;
     }
   };
 

lib/Sema/TypeCheckConstraints.cpp

@@ -342,9 +342,9 @@ class SyntacticDiagnosticWalker final : public ASTWalker {
   }
 
   MacroWalking getMacroWalkingBehavior() const override {
-    // Macro expansions will be walked when they're type-checked, not as
-    // part of the surrounding code.
-    return MacroWalking::None;
+    // We only want to walk macro arguments. Expansions will be walked when
+    // they're type-checked, not as part of the surrounding code.
+    return MacroWalking::Arguments;
   }
 
   PreWalkResult<Expr *> walkToExprPre(Expr *expr) override {

test/Macros/macro_misc_diags.swift

@@ -61,13 +61,16 @@ macro makeBinding<T>(_ x: T) = #externalMacro(module: "MacroPlugin", type: "Make
 @available(*, deprecated)
 func deprecatedFunc() -> Int { 0 }
 
-// FIXME: We also ought to be diagnosing the macro argument
+// Make sure we do MiscDiagnostics passes for both macro arguments and expansions.
+
 _ = #identity(Int)
 // CHECK-DIAG: @__swiftmacro_6Client0017Clientswift_yEEFcfMX[[@LINE-2]]{{.*}}identityfMf_.swift:1:1: error: expected member name or initializer call after type name
+// CHECK-DIAG: Client.swift:[[@LINE-2]]:15: error: expected member name or initializer call after type name
 
 _ = {
   _ = #identity(Int)
   // CHECK-DIAG: @__swiftmacro_6Client0017Clientswift_yEEFcfMX[[@LINE-2]]{{.*}}identityfMf0_.swift:1:1: error: expected member name or initializer call after type name
+  // CHECK-DIAG: Client.swift:[[@LINE-2]]:17: error: expected member name or initializer call after type name
 }
 
 _ = #identity(deprecatedFunc())
@@ -99,6 +102,14 @@ _ = #trailingClosure {
   // CHECK-DIAG: @__swiftmacro_6Client0017Clientswift_yEEFcfMX[[@LINE-4]]{{.*}}trailingClosurefMf_.swift:2:27: warning: trailing closure in this context is confusable with the body of the statement
 }
 
+func testOptionalToAny(_ y: Int?) {
+  _ = #trailingClosure {
+    let _: Any = y
+    // CHECK-DIAG: @__swiftmacro_6Client0017Clientswift_yEEFcfMX[[@LINE-3]]{{.*}}trailingClosurefMf_.swift:2:18: warning: expression implicitly coerced from 'Int?' to 'Any'
+    // CHECK-DIAG: Client.swift:[[@LINE-2]]:18: warning: expression implicitly coerced from 'Int?' to 'Any'
+  }
+}
+
 // rdar://138997009 - Make sure we don't crash in MiscDiagnostics' implicit
 // self diagnosis.
 struct rdar138997009 {
@@ -119,6 +130,7 @@ class rdar138997009_Class {
       _ = #trailingClosure {
         foo()
         // CHECK-DIAG: @__swiftmacro_6Client0017Clientswift_yEEFcfMX[[@LINE-3]]{{.*}}trailingClosurefMf_.swift:2:9: error: call to method 'foo' in closure requires explicit use of 'self' to make capture semantics explicit
+        // CHECK-DIAG: Client.swift:[[@LINE-2]]:9: error: call to method 'foo' in closure requires explicit use of 'self' to make capture semantics explicit
       }
     }
   }