Support #if swift(subminor-version), rdar://problem/28786959 / SR-2908.

Author: graydon

include/swift/Parse/Parser.h

@@ -122,6 +122,7 @@ class Parser {
   } InVarOrLetPattern = IVOLP_NotInVarOrLet;
 
   bool InPoundLineEnvironment = false;
+  bool InPoundIfEnvironment = false;
 
   LocalContext *CurLocalContext = nullptr;
 

lib/Parse/ParseExpr.cpp

@@ -1429,8 +1429,9 @@ ParserResult<Expr> Parser::parseExprPostfix(Diag<> ID, bool isExprBasic) {
         SourceLoc nameLoc = consumeToken(tok::integer_literal);
 
         // Don't allow '.<integer literal>' following a numeric literal
-        // expression.
-        if (Result.isNonNull() && isa<NumberLiteralExpr>(Result.get())) {
+        // expression (unless in #if env, for 1.2.3.4 version numbers)
+        if (!InPoundIfEnvironment &&
+            Result.isNonNull() && isa<NumberLiteralExpr>(Result.get())) {
           diagnose(nameLoc, diag::numeric_literal_numeric_member)
             .highlight(Result.get()->getSourceRange());
           continue;

lib/Parse/ParseStmt.cpp

@@ -1759,7 +1759,7 @@ Parser::evaluateConditionalCompilationExpr(Expr *condition) {
 ParserResult<Stmt> Parser::parseStmtIfConfig(BraceItemListKind Kind) {
   StructureMarkerRAII ParsingDecl(*this, Tok.getLoc(),
                                   StructureMarkerKind::IfConfig);
-
+  llvm::SaveAndRestore<bool> S(InPoundIfEnvironment, true);
   ConditionalCompilationExprState ConfigState;
   bool foundActive = false;
   SmallVector<IfConfigStmtClause, 4> Clauses;

test/Parse/ConditionalCompilation/language_version.swift

@@ -43,8 +43,7 @@
 #if swift("") // expected-error {{unexpected platform condition argument: expected a unary comparison, such as '>=2.2'}}
 #endif
 
-// We won't expect three version components to work for now.
-#if swift(>=2.2.1) // expected-error {{expected named member of numeric literal}}
+#if swift(>=2.2.1)
 #endif
 
 #if swift(>=2.0, *) // expected-error {{expected only one argument to platform condition}}