Fix ${x} variable syntax

Author: roblourens

src/Node/Expression/Variable.php

@@ -24,7 +24,7 @@ class Variable extends Expression {
     public function getName() {
         if (
             $this->name instanceof Token &&
-            $name = substr($this->name->getText($this->getFileContents()), 1)
+            $name = ltrim($this->name->getText($this->getFileContents()), '$')
         ) {
             return $name;
         }

src/Parser.php

@@ -1007,7 +1007,11 @@ private function parseStringLiteralExpression2($parentNode) {
                 case TokenKind::DollarOpenBraceToken:
                 case TokenKind::OpenBraceDollarToken:
                     $expression->children[] = $this->eat(TokenKind::DollarOpenBraceToken, TokenKind::OpenBraceDollarToken);
-                    $expression->children[] = $this->parseExpression($expression);
+                    if ($this->getCurrentToken()->kind === TokenKind::StringVarname) {
+                        $expression->children[] = $this->parseSimpleVariable($parentNode);
+                    } else {
+                        $expression->children[] = $this->parseExpression($expression);
+                    }
                     $expression->children[] = $this->eat(TokenKind::CloseBraceToken);
                     continue;
                 case $startQuoteKind = $expression->startQuote->kind:
@@ -2027,9 +2031,10 @@ private function parseSimpleVariableFn() {
                     $token->kind === TokenKind::OpenBraceToken ?
                         $this->parseBracedExpression($variable) :
                         $this->parseSimpleVariable($variable);
-            } elseif ($token->kind === TokenKind::VariableName) {
-                // TODO consider splitting into dollar and name
-                $variable->name = $this->eat(TokenKind::VariableName);
+            } elseif ($token->kind === TokenKind::VariableName || $token->kind === TokenKind::StringVarname) {
+                // TODO consider splitting into dollar and name.
+                // StringVarname is the variable name without $, used in a template string e.g. `"${foo}"`
+                $variable->name = $this->eat(TokenKind::VariableName, TokenKind::StringVarname);
             } else {
                 $variable->name = new MissingToken(TokenKind::VariableName, $token->fullStart);
             }

tests/cases/parser/stringLiteral3.php.tree

@@ -45,18 +45,13 @@
                                             "textLength": 2
                                         },
                                         {
-                                            "error": "MissingToken",
-                                            "kind": "Expression",
-                                            "textLength": 0
-                                        },
-                                        {
-                                            "error": "MissingToken",
-                                            "kind": "CloseBraceToken",
-                                            "textLength": 0
-                                        },
-                                        {
-                                            "kind": "StringVarname",
-                                            "textLength": 3
+                                            "Variable": {
+                                                "dollar": null,
+                                                "name": {
+                                                    "kind": "StringVarname",
+                                                    "textLength": 3
+                                                }
+                                            }
                                         },
                                         {
                                             "kind": "CloseBraceToken",