[Syntax] Parse WhileStmtSyntax nodes (#15186)

Author: harlanhaskins

lib/Parse/ParseStmt.cpp

@@ -1599,6 +1599,7 @@ ParserResult<Stmt> Parser::parseStmtGuard() {
 ///   stmt-while:
 ///     (identifier ':')? 'while' expr-basic stmt-brace
 ParserResult<Stmt> Parser::parseStmtWhile(LabeledStmtInfo LabelInfo) {
+  SyntaxContext->setCreateSyntax(SyntaxKind::WhileStmt);
   SourceLoc WhileLoc = consumeToken(tok::kw_while);
 
   Scope S(this, ScopeKind::WhileVars);

test/Syntax/Outputs/round_trip_parse_gen.swift.withkinds

@@ -319,7 +319,9 @@ func statementTests<FunctionSignature><ParameterClause>() </ParameterClause></Fu
   } </CodeBlock></CatchClause><CatchClause>catch <CodeBlock>{
   }</CodeBlock></CatchClause></DoStmt><RepeatWhileStmt>
   repeat <CodeBlock>{ } </CodeBlock>while <BooleanLiteralExpr>true</BooleanLiteralExpr></RepeatWhileStmt><RepeatWhileStmt>
-  LABEL: repeat <CodeBlock>{ } </CodeBlock>while <BooleanLiteralExpr>false</BooleanLiteralExpr></RepeatWhileStmt><DoStmt>
+  LABEL: repeat <CodeBlock>{ } </CodeBlock>while <BooleanLiteralExpr>false</BooleanLiteralExpr></RepeatWhileStmt><WhileStmt>
+  while <ConditionElement><BooleanLiteralExpr>true </BooleanLiteralExpr></ConditionElement><CodeBlock>{ }</CodeBlock></WhileStmt><WhileStmt>
+  LABEL: while <ConditionElement><BooleanLiteralExpr>true </BooleanLiteralExpr></ConditionElement><CodeBlock>{ }</CodeBlock></WhileStmt><DoStmt>
   LABEL: do <CodeBlock>{}</CodeBlock></DoStmt>
   LABEL: switch <IdentifierExpr>foo </IdentifierExpr>{
     case <ExpressionPattern><IntegerLiteralExpr>1</IntegerLiteralExpr></ExpressionPattern>:<FallthroughStmt>

test/Syntax/round_trip_parse_gen.swift

@@ -320,6 +320,8 @@ func statementTests() {
   }
   repeat { } while true
   LABEL: repeat { } while false
+  while true { }
+  LABEL: while true { }
   LABEL: do {}
   LABEL: switch foo {
     case 1: