[Parse] Fix parsing three-version-components in #if

* Narrow allowance of 3+ components numeric literal to condition part of the
  directive.
* Allow 3+ components in '#if' directive in decl list position as well.

Author: rintaro

lib/Parse/ParseDecl.cpp

@@ -3016,6 +3016,7 @@ ParserResult<IfConfigDecl> Parser::parseDeclIfConfig(ParseDeclOptions Flags) {
       ConfigState.setConditionActive(!foundActive);
     } else {
       // Evaluate the condition.
+      llvm::SaveAndRestore<bool> S(InPoundIfEnvironment, true);
       ParserResult<Expr> Result = parseExprSequence(diag::expected_expr,
                                                     /*isBasic*/true,
                                                     /*isForDirective*/true);

lib/Parse/ParseStmt.cpp

@@ -1771,7 +1771,6 @@ Parser::classifyConditionalCompilationExpr(Expr *condition,
 ParserResult<Stmt> Parser::parseStmtIfConfig(BraceItemListKind Kind) {
   StructureMarkerRAII ParsingDecl(*this, Tok.getLoc(),
                                   StructureMarkerKind::IfConfig);
-  llvm::SaveAndRestore<bool> S(InPoundIfEnvironment, true);
   SmallVector<IfConfigStmtClause, 4> Clauses;
 
   bool foundActive = false;
@@ -1785,6 +1784,7 @@ ParserResult<Stmt> Parser::parseStmtIfConfig(BraceItemListKind Kind) {
       ConfigState.setConditionActive(!foundActive);
     } else {
       // Evaluate the condition.
+      llvm::SaveAndRestore<bool> S(InPoundIfEnvironment, true);
       ParserResult<Expr> Result = parseExprSequence(diag::expected_expr,
                                                     /*basic*/true,
                                                     /*isForDirective*/true);

test/Parse/ConditionalCompilation/language_version.swift

@@ -44,8 +44,15 @@
 #endif
 
 #if swift(>=2.2.1)
+  _ = 2.2.1 // expected-error {{expected named member of numeric literal}}
 #endif
 
+class C {
+#if swift(>=2.2.1)
+  let val = 2.2.1 // expected-error {{expected named member of numeric literal}}
+#endif
+}
+
 #if swift(>=2.0, *) // expected-error {{expected only one argument to platform condition}}
 #endif