Fix minor bug in #sourceLocation on lex error (#19344)

Fix a minor bug in the implementation of #sourceLocation when the
directive is succeeded by token that gives an error during lexing.
The error will be reported with the wrong location. This is because
lexing of the next token occurs immediately on consuming the last
token of the directive which is before the virtual file is set up to have
the location take effect.

Resolved by moving consumption of directives last token to the end
of the function.

Author: johnno1962

lib/Parse/ParseDecl.cpp

@@ -3583,7 +3583,6 @@ ParserStatus Parser::parseLineDirective(bool isLine) {
 
   unsigned StartLine = 0;
   Optional<StringRef> Filename;
-  const char *LastTokTextEnd;
   if (!isLine) {
     // #sourceLocation()
     // #sourceLocation(file: "foo", line: 42)
@@ -3640,10 +3639,10 @@ ParserStatus Parser::parseLineDirective(bool isLine) {
       consumeToken(tok::integer_literal);
     }
 
-    LastTokTextEnd = Tok.getText().end();
-    if (parseToken(tok::r_paren, diag::sourceLocation_expected, ")"))
+    if (Tok.isNot(tok::r_paren)) {
+      diagnose(Tok, diag::sourceLocation_expected, ")");
       return makeParserError();
-    
+    }
   } else {  // Legacy #line syntax.
 
     // #line\n returns to the main buffer.
@@ -3679,10 +3678,10 @@ ParserStatus Parser::parseLineDirective(bool isLine) {
                                                  "#line");
     if (!Filename.hasValue())
       return makeParserError();
-    LastTokTextEnd = Tok.getText().end();
-    consumeToken(tok::string_literal);
   }
-  
+
+  const char *LastTokTextEnd = Tok.getText().end();
+
   // Skip over trailing whitespace and a single \n to the start of the next
   // line.
   while (*LastTokTextEnd == ' ' || *LastTokTextEnd == '\t')
@@ -3703,6 +3702,9 @@ ParserStatus Parser::parseLineDirective(bool isLine) {
                                              Filename.getValue(), LineOffset);
   assert(isNewFile);(void)isNewFile;
 
+  // Lexing of next token must be deferred until after virtual file setup.
+  consumeToken(isLine ? tok::string_literal : tok::r_paren);
+
   InPoundLineEnvironment = true;
   return makeParserSuccess();
 }

test/Parse/line-directive.swift

@@ -1,4 +1,5 @@
 // RUN: %target-typecheck-verify-swift
+// RUN: not %target-swift-frontend -c %s 2>&1 | %FileCheck %s
 
 let x = 0 // We need this because of the #sourceLocation-ends-with-a-newline requirement.
 
@@ -53,3 +54,9 @@ enum E {
     case C, D
 #sourceLocation()
 }
+
+#sourceLocation(file: "sr8772.swift", line: 400)
+2., 3
+// CHECK: sr8772.swift:400:2: error: expected member name following '.'
+// CHECK: sr8772.swift:400:3: error: consecutive statements on a line must be separated by ';'
+// CHECK: sr8772.swift:400:3: error: expected expression