[DiagnosticsQoI] SR-3600: Better recovery for trying to name an initializer, deinitializer, or subscript

- Restrict this diagnostic to identifiers that are followed by a left paren.

Author: matthewcarroll

lib/Parse/ParseDecl.cpp

@@ -5517,10 +5517,8 @@ parseDeclDeinit(ParseDeclOptions Flags, DeclAttributes &Attributes) {
     if (!Tok.is(tok::l_brace) && !isInSILMode()) {
       if (Tok.is(tok::identifier)) {
         diagnose(Tok, diag::destructor_has_name).fixItRemove(Tok.getLoc());
-      }
-      else {
+      } else
         diagnose(Tok, diag::expected_lbrace_destructor);
-      }
       return nullptr;
     }
   }

lib/Parse/ParsePattern.cpp

@@ -483,12 +483,14 @@ Parser::parseSingleParameterClause(ParameterContextKind paramContext,
       diagID = diag::func_decl_without_paren;
       break;
     case ParameterContextKind::Subscript:
-      skipIdentifier = Tok.is(tok::identifier);
+      skipIdentifier = Tok.is(tok::identifier) &&
+                       peekToken().is(tok::l_paren);
       diagID = skipIdentifier ? diag::subscript_has_name
                               : diag::expected_lparen_subscript;
       break;
     case ParameterContextKind::Initializer:
-      skipIdentifier = Tok.is(tok::identifier);
+      skipIdentifier = Tok.is(tok::identifier) &&
+                       peekToken().is(tok::l_paren);
       diagID = skipIdentifier ? diag::initializer_has_name
                               : diag::expected_lparen_initializer;
       break;

test/Parse/recovery.swift

@@ -541,6 +541,18 @@ struct InitializerWithName {
   init x() {} // expected-error {{initializers cannot have a name}} {{8-9=}}
 }
 
+struct InitializerWithNameAndParam {
+  init a(b: Int) {} // expected-error {{initializers cannot have a name}} {{8-9=}}
+}
+
+struct InitializerWithLabels {
+  init c d: Int {}
+  // expected-error @-1 {{expected '(' for initializer parameters}}
+  // expected-error @-2 {{expected declaration}}
+  // expected-error @-3 {{consecutive declarations on a line must be separated by ';'}}
+  // expected-note @-5 {{in declaration of 'InitializerWithLabels'}}
+}
+
 // rdar://20337695
 func f1() {
 

test/Parse/subscripting.swift

@@ -81,7 +81,7 @@ _ = y2[0] // expected-error{{cannot use mutating getter on immutable value: 'y2'
 
 // Parsing errors
 struct A0 {
-  subscript // expected-error {{subscripts cannot have a name}} {{5-7=}}
+  subscript // expected-error {{expected '(' for subscript parameters}}
     i : Int
      -> Int {
     get {
@@ -175,4 +175,23 @@ struct A8 {
       stored = value
     }
   }
+
+struct A9 {
+  subscript x() -> Int { // expected-error {{subscripts cannot have a name}} {{13-14=}}
+    return 0
+  }
+}
+
+struct A10 {
+  subscript x(i: Int) -> Int { // expected-error {{subscripts cannot have a name}} {{13-14=}}
+    return 0
+  }
+}
+
+struct A11 {
+  subscript x y : Int -> Int { // expected-error {{expected '(' for subscript parameters}}
+    return 0
+  }
+}
+
 } // expected-error{{extraneous '}' at top level}} {{1-3=}}