[Parse] Restrict parsing integer types in certain contexts

include/swift/Parse/Parser.h

@@ -1435,6 +1435,11 @@ class Parser {
   ParserResult<TypeRepr> parseTypeSimple(
       Diag<> MessageID, ParseTypeReason reason);
 
+  ParserResult<TypeRepr> parseTypeOrValue();
+  ParserResult<TypeRepr> parseTypeOrValue(Diag<> MessageID,
+                          ParseTypeReason reason = ParseTypeReason::Unspecified,
+                          bool fromASTGen = false);
+
   /// Parse layout constraint.
   LayoutConstraint parseLayoutConstraint(Identifier LayoutConstraintID);
 

lib/Parse/ParseDecl.cpp

@@ -4116,7 +4116,7 @@ ParserStatus Parser::parseNewDeclAttribute(DeclAttributes &Attributes,
         return makeParserSuccess();
       }
 
-      auto countType = parseType(diag::expected_type);
+      auto countType = parseTypeOrValue(diag::expected_type);
       if (countType.isNull()) {
         return makeParserSuccess();
       }

lib/Parse/ParseGeneric.cpp

@@ -317,7 +317,9 @@ ParserStatus Parser::parseGenericWhereClause(
 
     // Parse the leading type. It doesn't necessarily have to be just a type
     // identifier if we're dealing with a same-type constraint.
-    ParserResult<TypeRepr> FirstType = parseType();
+    //
+    // Note: This can be a value type, e.g. '123 == N' or 'N == 123'.
+    ParserResult<TypeRepr> FirstType = parseTypeOrValue();
 
     if (FirstType.hasCodeCompletion()) {
       Status.setHasCodeCompletionAndIsError();
@@ -377,7 +379,9 @@ ParserStatus Parser::parseGenericWhereClause(
       SourceLoc EqualLoc = consumeToken();
 
       // Parse the second type.
-      ParserResult<TypeRepr> SecondType = parseType();
+      //
+      // Note: This can be a value type, e.g. '123 == N' or 'N == 123'.
+      ParserResult<TypeRepr> SecondType = parseTypeOrValue();
       Status |= SecondType;
       if (SecondType.isNull())
         SecondType = makeParserResult(ErrorTypeRepr::create(Context, PreviousLoc));

lib/Parse/ParseType.cpp

@@ -175,12 +175,6 @@ ParserResult<TypeRepr> Parser::parseTypeSimple(
     tildeLoc = consumeToken();
   }
 
-  // Eat any '-' preceding integer literals.
-  SourceLoc minusLoc;
-  if (Tok.isMinus() && peekToken().is(tok::integer_literal)) {
-    minusLoc = consumeToken();
-  }
-
   switch (Tok.getKind()) {
   case tok::kw_Self:
   case tok::identifier:
@@ -237,12 +231,6 @@ ParserResult<TypeRepr> Parser::parseTypeSimple(
     }
     return makeParserCodeCompletionResult<TypeRepr>(
         ErrorTypeRepr::create(Context, consumeToken(tok::code_complete)));
-  case tok::integer_literal: {
-    auto text = copyAndStripUnderscores(Tok.getText());
-    auto loc = consumeToken(tok::integer_literal);
-    ty = makeParserResult(new (Context) IntegerTypeRepr(text, loc, minusLoc));
-    break;
-  }
   case tok::l_square: {
     ty = parseTypeCollection();
     break;
@@ -739,7 +727,8 @@ ParserStatus Parser::parseGenericArguments(SmallVectorImpl<TypeRepr *> &Args,
   // variadic generic types.
   if (!startsWithGreater(Tok)) {
     while (true) {
-      ParserResult<TypeRepr> Ty = parseType(diag::expected_type);
+      // Note: This can be a value type, e.g. 'Vector<3, Int>'.
+      ParserResult<TypeRepr> Ty = parseTypeOrValue(diag::expected_type);
       if (Ty.isNull() || Ty.hasCodeCompletion()) {
         // Skip until we hit the '>'.
         RAngleLoc = skipUntilGreaterInTypeList();
@@ -1481,6 +1470,31 @@ Parser::parseTypeImplicitlyUnwrappedOptional(ParserResult<TypeRepr> base) {
   return makeParserResult(ParserStatus(base), TyR);
 }
 
+ParserResult<TypeRepr> Parser::parseTypeOrValue() {
+  return parseTypeOrValue(diag::expected_type);
+}
+
+ParserResult<TypeRepr> Parser::parseTypeOrValue(Diag<> MessageID,
+                                                ParseTypeReason reason,
+                                                bool fromASTGen) {
+  // Eat any '-' preceding integer literals.
+  SourceLoc minusLoc;
+  if (Tok.isMinus() && peekToken().is(tok::integer_literal)) {
+    minusLoc = consumeToken();
+  }
+
+  // Attempt to parse values first. Right now the only value that can be parsed
+  // as a type are integers.
+  if (Tok.is(tok::integer_literal)) {
+    auto text = copyAndStripUnderscores(Tok.getText());
+    auto loc = consumeToken(tok::integer_literal);
+    return makeParserResult(new (Context) IntegerTypeRepr(text, loc, minusLoc));
+  }
+
+  // Otherwise, attempt to parse a regular type.
+  return parseType(MessageID, reason, fromASTGen);
+}
+
 //===----------------------------------------------------------------------===//
 // Speculative type list parsing
 //===----------------------------------------------------------------------===//

test/Parse/integer_types.swift

@@ -1,8 +1,12 @@
 // RUN: %target-typecheck-verify-swift
 
-let a: 123 // expected-error {{integer unexpectedly used in a type position}}
+let a: 123 // expected-error {{consecutive statements on a line must be separated by ';'}}
+           // expected-error@-1 {{expected type}}
+           // expected-warning@-2 {{integer literal is unused}}
 
-let b: -123 // expected-error {{integer unexpectedly used in a type position}}
+let b: -123 // expected-error {{consecutive statements on a line must be separated by ';'}}
+           // expected-error@-1 {{expected type}}
+           // expected-warning@-2 {{integer literal is unused}}
 
 let c: -Int // expected-error {{expected type}}
             // expected-error@-1 {{consecutive statements on a line must be separated by ';'}}
@@ -30,3 +34,19 @@ let f = Generic<-Int>.self // expected-error {{generic parameter 'T' could not b
                            // expected-error@-1 {{missing whitespace between '<' and '-' operators}}
                            // expected-error@-2 {{'>' is not a postfix unary operator}}
                            // expected-note@-3 {{explicitly specify the generic arguments to fix this issue}}
+
+let g: 123.Type // expected-error {{consecutive statements on a line must be separated by ';'}}
+                // expected-error@-1 {{expected type}}
+                // expected-error@-2 {{value of type 'Int' has no member 'Type'}}
+
+let h: 123.Protocol // expected-error {{consecutive statements on a line must be separated by ';'}}
+                    // expected-error@-1 {{expected type}}
+                    // expected-error@-2 {{value of type 'Int' has no member 'Protocol'}}
+
+let i: 123? // expected-error {{consecutive statements on a line must be separated by ';'}}
+            // expected-error@-1 {{expected type}}
+            // expected-error@-2 {{cannot use optional chaining on non-optional value of type 'Int'}}
+
+let j: 123! // expected-error {{consecutive statements on a line must be separated by ';'}}
+            // expected-error@-1 {{expected type}}
+            // expected-error@-2 {{cannot force unwrap value of non-optional type 'Int'}}

test/Sema/value_generics.swift

@@ -49,18 +49,21 @@ struct Generic<T: ~Copyable & ~Escapable> {}
 struct GenericWithIntParam<T: ~Copyable & ~Escapable, let N: Int> {}
 
 extension Generic where T == 123 {} // expected-error {{cannot constrain type parameter 'T' to be integer '123'}}
-extension Generic where T == 123.Type {} // expected-error {{integer unexpectedly used in a type position}}
+extension Generic where T == 123.Type {} // expected-error {{cannot constrain type parameter 'T' to be integer '123'}}
+                                         // expected-error@-1 {{expected '{' in extension}}
+extension Generic where T == 123? {} // expected-error {{cannot constrain type parameter 'T' to be integer '123'}}
+                                     // expected-error@-1 {{expected '{' in extension}}
 
 func f(_: Generic<123>) {} // expected-error {{integer unexpectedly used in a type position}}
 func g<let N: Int>(_: Generic<N>) {} // expected-error {{cannot use value type 'N' for generic argument 'T'}}
-func h(_: (Int, 123)) {} // expected-error {{integer unexpectedly used in a type position}}
-func i(_: () -> 123) {} // expected-error {{integer unexpectedly used in a type position}}
+func h(_: (Int, 123)) {} // expected-error {{expected type}}
+func i(_: () -> 123) {} // expected-error {{expected type}}
 func j(_: (A<123>) -> ()) {} // OK
-func k(_: some 123) {} // expected-error {{integer unexpectedly used in a type position}}
+func k(_: some 123) {} // expected-error {{expected parameter type following ':'}}
 func l(_: GenericWithIntParam<123, Int>) {} // expected-error {{cannot pass type 'Int' as a value for generic value 'N'}}
 func m(_: GenericWithIntParam<Int, 123>) {} // OK
 
-typealias One = 1 // expected-error {{integer unexpectedly used in a type position}}
+typealias One = 1 // expected-error {{expected type in type alias declaration}}
 
 struct B<let N: UInt8> {} // expected-error {{'UInt8' is not a supported value type for 'N'}}