[Parse] Reject trailing closures on literals (#7202)

`1 { }` was parsed as a call expression with a trailing closure. This made the diagnostics for `var x = 1 { get { ... } }` extremely bad. Resolves SR-3671.

Author: jtbandes

lib/Parse/ParseExpr.cpp

@@ -1581,8 +1581,14 @@ ParserResult<Expr> Parser::parseExprPostfix(Diag<> ID, bool isExprBasic) {
     if (Tok.is(tok::l_brace) && isValidTrailingClosure(isExprBasic, *this)) {
       // FIXME: if Result has a trailing closure, break out.
 
+      // Stop after literal expressions, which may never have trailing closures.
+      const auto *callee = Result.get();
+      if (isa<LiteralExpr>(callee) || isa<CollectionExpr>(callee) ||
+          isa<TupleExpr>(callee))
+        break;
+
       ParserResult<Expr> closure =
-        parseTrailingClosure(Result.get()->getSourceRange());
+        parseTrailingClosure(callee->getSourceRange());
       if (closure.isNull()) return nullptr;
 
       // Trailing closure implicitly forms a call.

test/Constraints/closures.swift

@@ -64,19 +64,21 @@ func test13811882() {
 
 
 // <rdar://problem/21544303> QoI: "Unexpected trailing closure" should have a fixit to insert a 'do' statement
+// <https://bugs.swift.org/browse/SR-3671>
 func r21544303() {
-  var inSubcall = true
+  let val = true
+  var inSubcall = val
   {   // expected-error {{expected 'do' keyword to designate a block of statements}} {{3-3=do }}
   }
   inSubcall = false
 
   // This is a problem, but isn't clear what was intended.
-  var somethingElse = true { // expected-error {{cannot call value of non-function type 'Bool'}}
+  var somethingElse = val { // expected-error {{cannot call value of non-function type 'Bool'}}
   }
   inSubcall = false
 
   var v2 : Bool = false
-  v2 = true
+  v2 = val
   {  // expected-error {{expected 'do' keyword to designate a block of statements}}
   }
 }

test/Parse/recovery.swift

@@ -91,7 +91,7 @@ func missingControllingExprInIf() {
   if { true } { // expected-error {{missing condition in an 'if' statement}} expected-error {{braced block of statements is an unused closure}} expected-error{{expression resolves to an unused function}} expected-error{{consecutive statements on a line must be separated by ';'}} {{14-14=;}} expected-warning {{boolean literal is unused}}
   }
 
-  if { true }() { // expected-error {{missing condition in an 'if' statement}} expected-error{{consecutive statements on a line must be separated by ';'}} {{14-14=;}} expected-error{{cannot call value of non-function type '()'}} expected-warning {{boolean literal is unused}}
+  if { true }() { // expected-error {{missing condition in an 'if' statement}} expected-error {{braced block of statements is an unused closure}} expected-error 2 {{consecutive statements on a line must be separated by ';'}} expected-error {{expression resolves to an unused function}} expected-warning {{boolean literal is unused}}
   }
 
   // <rdar://problem/18940198>
@@ -113,7 +113,7 @@ func missingControllingExprInWhile() {
   while { true } { // expected-error {{missing condition in a 'while' statement}} expected-error {{braced block of statements is an unused closure}} expected-error{{expression resolves to an unused function}} expected-error{{consecutive statements on a line must be separated by ';'}} {{17-17=;}} expected-warning {{boolean literal is unused}}
   }
 
-  while { true }() { // expected-error {{missing condition in a 'while' statement}} expected-error{{consecutive statements on a line must be separated by ';'}} {{17-17=;}} expected-error{{cannot call value of non-function type '()'}} expected-warning {{boolean literal is unused}}
+  while { true }() { // expected-error {{missing condition in a 'while' statement}} expected-error {{braced block of statements is an unused closure}} expected-error 2 {{consecutive statements on a line must be separated by ';'}} expected-error {{expression resolves to an unused function}} expected-warning {{boolean literal is unused}}
   }
 
   // <rdar://problem/18940198>
@@ -223,7 +223,7 @@ func missingControllingExprInSwitch() {
     case _: return // expected-error{{'case' label can only appear inside a 'switch' statement}}
   }
 
-  switch { 42 }() { // expected-error {{expected expression in 'switch' statement}} expected-error {{all statements inside a switch must be covered by a 'case' or 'default'}} expected-error {{consecutive statements on a line must be separated by ';'}} {{16-16=;}} expected-error {{cannot call value of non-function type '()'}}
+  switch { 42 }() { // expected-error {{expected expression in 'switch' statement}} expected-error {{all statements inside a switch must be covered by a 'case' or 'default'}} expected-error {{braced block of statements is an unused closure}} expected-error 2 {{consecutive statements on a line must be separated by ';'}} expected-error {{expression resolves to an unused function}}
     case _: return // expected-error{{'case' label can only appear inside a 'switch' statement}}
   }
 }

test/Sema/immutability.swift

@@ -7,8 +7,8 @@ let bad_property_1: Int {    // expected-error {{'let' declarations cannot be co
     return 42
   }
 }
-let bad_property_2: Int = 0 {
-  get { // expected-error {{use of unresolved identifier 'get'}}
+let bad_property_2: Int = 0 { // expected-error {{'let' declarations cannot be computed properties}} expected-error {{variable with getter/setter cannot have an initial value}}
+  get {
     return 42
   }
 }

test/decl/var/properties.swift

@@ -120,20 +120,19 @@ var x15: Int {
 
 // Disambiguated as stored property with a trailing closure in the initializer.
 //
-// FIXME: QoI could be much better here.
-var disambiguateGetSet1a: Int = 0 {
-  get {} // expected-error {{use of unresolved identifier 'get'}}
+var disambiguateGetSet1a: Int = 0 { // expected-error {{variable with getter/setter cannot have an initial value}}
+  get {}
 }
-var disambiguateGetSet1b: Int = 0 {
-  get { // expected-error {{use of unresolved identifier 'get'}}
+var disambiguateGetSet1b: Int = 0 { // expected-error {{variable with getter/setter cannot have an initial value}}
+  get {
     return 42
   }
 }
-var disambiguateGetSet1c: Int = 0 {
-  set {} // expected-error {{use of unresolved identifier 'set'}}
+var disambiguateGetSet1c: Int = 0 { // expected-error {{variable with getter/setter cannot have an initial value}}
+  set {} // expected-error {{variable with a setter must also have a getter}}
 }
-var disambiguateGetSet1d: Int = 0 {
-  set(newValue) {} // expected-error {{use of unresolved identifier 'set'}} expected-error {{use of unresolved identifier 'newValue'}}
+var disambiguateGetSet1d: Int = 0 { // expected-error {{variable with getter/setter cannot have an initial value}}
+  set(newValue) {} // expected-error {{variable with a setter must also have a getter}}
 }
 
 // Disambiguated as stored property with a trailing closure in the initializer.
@@ -199,7 +198,7 @@ func disambiguateGetSet4Attr() {
 }
 
 // Disambiguated as stored property with a trailing closure in the initializer.
-var disambiguateImplicitGet1: Int = 0 { // expected-error {{cannot call value of non-function type 'Int'}}
+var disambiguateImplicitGet1: Int = 0 { // expected-error {{variable with getter/setter cannot have an initial value}}
   return 42
 }
 var disambiguateImplicitGet2: Int = takeIntTrailingClosure {

test/expr/closure/trailing.swift

@@ -37,6 +37,30 @@ func notPostfix() {
   _ = 1 + takeFunc { $0 }
 }
 
+func notLiterals() {
+  struct SR3671 { // <https://bugs.swift.org/browse/SR-3671>
+    var v: Int = 1 { // expected-error {{variable with getter/setter cannot have an initial value}}
+      get {
+        return self.v
+      }
+    }
+  }
+
+  var x: Int? = nil { get { } } // expected-error {{variable with getter/setter cannot have an initial value}}
+  _ = 1 {}
+  // expected-error@-1 {{consecutive statements on a line must be separated by ';'}}
+  // expected-error@-2 {{braced block of statements is an unused closure}} expected-error@-2 {{expression resolves to an unused function}}
+  _ = "hello" {}
+  // expected-error@-1 {{consecutive statements on a line must be separated by ';'}}
+  // expected-error@-2 {{braced block of statements is an unused closure}} expected-error@-2 {{expression resolves to an unused function}}
+  _ = [42] {}
+  // expected-error@-1 {{consecutive statements on a line must be separated by ';'}}
+  // expected-error@-2 {{braced block of statements is an unused closure}} expected-error@-2 {{expression resolves to an unused function}}
+  _ = (6765, 10946, 17711) {}
+  // expected-error@-1 {{consecutive statements on a line must be separated by ';'}}
+  // expected-error@-2 {{braced block of statements is an unused closure}} expected-error@-2 {{expression resolves to an unused function}}
+}
+
 class C {
   func map(_ x: (Int) -> Int) -> C { return self }
   func filter(_ x: (Int) -> Bool) -> C { return self }