initial checkin of SkSL compiler

src/sksl/SkSLParser.cpp

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+ 
+#include "stdio.h"
+#include "SkSLParser.h"
+#include "SkSLToken.h"
+
+#define register
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunneeded-internal-declaration"
+#endif
+#include "lex.sksl.c"
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+#undef register
+
+#include "ast/SkSLASTBinaryExpression.h"
+#include "ast/SkSLASTBlock.h"
+#include "ast/SkSLASTBoolLiteral.h"
+#include "ast/SkSLASTBreakStatement.h"
+#include "ast/SkSLASTCallSuffix.h"
+#include "ast/SkSLASTContinueStatement.h"
+#include "ast/SkSLASTDiscardStatement.h"
+#include "ast/SkSLASTDoStatement.h"
+#include "ast/SkSLASTExpression.h"
+#include "ast/SkSLASTExpressionStatement.h"
+#include "ast/SkSLASTExtension.h"
+#include "ast/SkSLASTFieldSuffix.h"
+#include "ast/SkSLASTFloatLiteral.h"
+#include "ast/SkSLASTForStatement.h"
+#include "ast/SkSLASTFunction.h"
+#include "ast/SkSLASTIdentifier.h"
+#include "ast/SkSLASTIfStatement.h"
+#include "ast/SkSLASTIndexSuffix.h"
+#include "ast/SkSLASTInterfaceBlock.h"
+#include "ast/SkSLASTIntLiteral.h"
+#include "ast/SkSLASTParameter.h"
+#include "ast/SkSLASTPrefixExpression.h"
+#include "ast/SkSLASTReturnStatement.h"
+#include "ast/SkSLASTStatement.h"
+#include "ast/SkSLASTSuffixExpression.h"
+#include "ast/SkSLASTTernaryExpression.h"
+#include "ast/SkSLASTType.h"
+#include "ast/SkSLASTVarDeclaration.h"
+#include "ast/SkSLASTVarDeclarationStatement.h"
+#include "ast/SkSLASTWhileStatement.h"
+#include "ir/SkSLSymbolTable.h"
+
+namespace SkSL {
+
+Parser::Parser(std::string text, SymbolTable& types, ErrorReporter& errors) 
+: fPushback(Position(-1, -1), Token::INVALID_TOKEN, "")
+, fTypes(types)
+, fErrors(errors) {
+    sksllex_init(&fScanner);
+    fBuffer = sksl_scan_string(text.c_str(), fScanner);
+    skslset_lineno(1, fScanner);
+
+    if (false) {
+        // avoid unused warning
+        yyunput(0, nullptr, fScanner);
+    }
+}
+
+Parser::~Parser() {
+    sksl_delete_buffer(fBuffer, fScanner);
+}
+
+/* (precision | directive | declaration)* END_OF_FILE */
+std::vector<std::unique_ptr<ASTDeclaration>> Parser::file() {
+    std::vector<std::unique_ptr<ASTDeclaration>> result;
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::END_OF_FILE:
+                return result;
+            case Token::PRECISION:
+                this->precision();
+                break;
+            case Token::DIRECTIVE: {
+                std::unique_ptr<ASTDeclaration> decl = this->directive();
+                if (decl != nullptr) {
+                    result.push_back(std::move(decl));
+                }
+                break;
+            }
+            default: {
+                std::unique_ptr<ASTDeclaration> decl = this->declaration();
+                if (decl == nullptr) {
+                    continue;
+                }
+                result.push_back(std::move(decl));
+            }
+        }
+    }
+}
+
+Token Parser::nextToken() {
+    if (fPushback.fKind != Token::INVALID_TOKEN) {
+        Token result = fPushback;
+        fPushback.fKind = Token::INVALID_TOKEN;
+        fPushback.fText = "";
+        return result;
+    }
+    int token = sksllex(fScanner);
+    return Token(Position(skslget_lineno(fScanner), -1), (Token::Kind) token, 
+                 token == Token::END_OF_FILE ? "<end of file>" : 
+                                               std::string(skslget_text(fScanner)));
+}
+
+void Parser::pushback(Token t) {
+    ASSERT(fPushback == Token::INVALID_TOKEN);
+    fPushback = t;
+}
+
+Token Parser::peek() {
+    fPushback = this->nextToken();
+    return fPushback;
+}
+
+bool Parser::expect(Token::Kind kind, std::string expected, Token* result) {
+    Token next = this->nextToken();
+    if (next.fKind == kind) {
+        if (result != nullptr) {
+            *result = next;
+        }
+        return true;
+    } else {
+        this->error(next.fPosition, "expected " + expected + ", but found '" + next.fText + "'");
+        return false;
+    }
+}
+
+void Parser::error(Position p, std::string msg) {
+    fErrors.error(p, msg);
+}
+
+bool Parser::isType(std::string name) {
+    return fTypes[name] != nullptr;
+}
+
+/* PRECISION (LOWP | MEDIUMP | HIGHP) type SEMICOLON */
+void Parser::precision() {
+    if (!this->expect(Token::PRECISION, "'precision'")) {
+        return;
+    }
+    Token p = this->nextToken();
+    switch (p.fKind) {
+        case Token::LOWP: // fall through
+        case Token::MEDIUMP: // fall through
+        case Token::HIGHP:
+            // ignored for now
+            break;
+        default:
+            this->error(p.fPosition, "expected 'lowp', 'mediump', or 'highp', but found '" + 
+                                     p.fText + "'");
+            return;
+    }
+    if (this->type() == nullptr) {
+        return;
+    }
+    this->expect(Token::SEMICOLON, "';'");
+}
+
+/* DIRECTIVE(#version) INT_LITERAL | DIRECTIVE(#extension) IDENTIFIER COLON IDENTIFIER */
+std::unique_ptr<ASTDeclaration> Parser::directive() {
+    Token start;
+    if (!this->expect(Token::DIRECTIVE, "a directive", &start)) {
+        return nullptr;
+    }
+    if (start.fText == "#version") {
+        this->expect(Token::INT_LITERAL, "a version number");
+        // ignored for now
+        return nullptr;
+    } else if (start.fText == "#extension") {
+        Token name;
+        if (!this->expect(Token::IDENTIFIER, "an identifier", &name)) {
+            return nullptr;
+        }
+        if (!this->expect(Token::COLON, "':'")) {
+            return nullptr;
+        }
+        // FIXME: need to start paying attention to this token
+        if (!this->expect(Token::IDENTIFIER, "an identifier")) {
+            return nullptr;
+        }
+        return std::unique_ptr<ASTDeclaration>(new ASTExtension(start.fPosition, 
+                                                                std::move(name.fText)));
+    } else {
+        this->error(start.fPosition, "unsupported directive '" + start.fText + "'");
+        return nullptr;
+    }
+}
+
+/* modifiers (structVarDeclaration | type IDENTIFIER ((LPAREN parameter 
+   (COMMA parameter)* RPAREN (block | SEMICOLON)) | SEMICOLON) | interfaceBlock) */
+std::unique_ptr<ASTDeclaration> Parser::declaration() {
+    ASTModifiers modifiers = this->modifiers();
+    Token lookahead = this->peek();
+    if (lookahead.fKind == Token::IDENTIFIER && !this->isType(lookahead.fText)) {
+        // we have an identifier that's not a type, could be the start of an interface block
+        return this->interfaceBlock(modifiers);
+    }
+    if (lookahead.fKind == Token::STRUCT) {
+        return this->structVarDeclaration(modifiers);
+    }
+    std::unique_ptr<ASTType> type(this->type());
+    if (!type) {
+        return nullptr;
+    }
+    if (type->fKind == ASTType::kStruct_Kind && peek().fKind == Token::SEMICOLON) {
+        this->nextToken();
+        return nullptr;
+    }
+    Token name;
+    if (!this->expect(Token::IDENTIFIER, "an identifier", &name)) {
+        return nullptr;
+    }
+    if (!modifiers.fFlags && this->peek().fKind == Token::LPAREN) {
+        this->nextToken();
+        std::vector<std::unique_ptr<ASTParameter>> parameters;
+        while (this->peek().fKind != Token::RPAREN) {
+            if (parameters.size() > 0) {
+                if (!this->expect(Token::COMMA, "','")) {
+                    return nullptr;
+                }
+            }
+            std::unique_ptr<ASTParameter> parameter = this->parameter();
+            if (!parameter) {
+                return nullptr;
+            }
+            parameters.push_back(std::move(parameter));
+        }
+        this->nextToken();
+        std::unique_ptr<ASTBlock> body;
+        if (this->peek().fKind == Token::SEMICOLON) {
+            this->nextToken();
+        } else {
+            body = this->block();
+            if (!body) {
+                return nullptr;
+            }
+        }
+        return std::unique_ptr<ASTDeclaration>(new ASTFunction(name.fPosition, std::move(type), 
+                                                               std::move(name.fText), 
+                                                               std::move(parameters), 
+                                                               std::move(body)));
+    } else {
+        return this->varDeclarationEnd(modifiers, std::move(type), name.fText);
+    }
+}
+
+/* modifiers type IDENTIFIER (EQ expression)? (COMMA IDENTIFER (EQ expression)?)* SEMICOLON */
+std::unique_ptr<ASTVarDeclaration> Parser::varDeclaration() {
+    ASTModifiers modifiers = this->modifiers();
+    std::unique_ptr<ASTType> type(this->type());
+    if (!type) {
+        return nullptr;
+    }
+    Token name;
+    if (!this->expect(Token::IDENTIFIER, "an identifier", &name)) {
+        return nullptr;
+    }
+    return this->varDeclarationEnd(modifiers, std::move(type), std::move(name.fText));
+}
+
+/* STRUCT IDENTIFIER LBRACE varDeclaration* RBRACE */
+std::unique_ptr<ASTType> Parser::structDeclaration() {
+    if (!this->expect(Token::STRUCT, "'struct'")) {
+        return nullptr;
+    }
+    Token name;
+    if (!this->expect(Token::IDENTIFIER, "an identifier", &name)) {
+        return nullptr;
+    }
+    if (!this->expect(Token::LBRACE, "'{'")) {
+        return nullptr;
+    }
+    std::vector<Type::Field> fields;
+    while (this->peek().fKind != Token::RBRACE) {
+        std::unique_ptr<ASTVarDeclaration> decl = this->varDeclaration();
+        if (decl == nullptr) {
+            return nullptr;
+        }
+        for (size_t i = 0; i < decl->fNames.size(); i++) {
+            std::shared_ptr<Type> type = std::static_pointer_cast<Type>(fTypes[decl->fType->fName]);
+            for (int j = (int) decl->fSizes[i].size() - 1; j >= 0; j--) {

[dogben, 2016/06/23 15:25:12]

nit: It seems odd that for fields we reverse the array dimensions in the parser
and check that the sizes are constant, but for variables and parameters, we
reverse the array dimensions in the IRGenerator, and check that parameter sizes
are constant.

[ethannicholas, 2016/06/24 21:23:09]

I agree that it's not ideal, but did not feel it was worth the refactoring
effort at the time to fix it. It just worked out that (without major refactoring
effort) I had to know the array sizes at this point in order to create the Type,
whereas the other cases do not require the Type to be created so early. I will
definitely reexamine this in the future, but don't think it's worth it right
this second.

+                if (decl->fSizes[i][j]->fKind == ASTExpression::kInt_Kind) {
+                    this->error(decl->fPosition, "array size in struct field must be a constant");
+                }
+                uint64_t columns = ((ASTIntLiteral&) *decl->fSizes[i][j]).fValue;
+                std::string name = type->name() + "[" + to_string(columns) + "]";
+                type = std::shared_ptr<Type>(new Type(name, Type::kArray_Kind, type, 
+                                             (int) columns));
+            }
+            fields.push_back(Type::Field(decl->fModifiers, decl->fNames[i], type));
+            if (decl->fValues[i] != nullptr) {
+                this->error(decl->fPosition, "initializers are not permitted on struct fields");
+            }
+        }
+    }
+    if (!this->expect(Token::RBRACE, "'}'")) {
+        return nullptr;
+    }
+    std::shared_ptr<Type> type(new Type(name.fText, fields));
+    fTypes.add(type->fName, type);
+    return std::unique_ptr<ASTType>(new ASTType(name.fPosition, type->fName, 
+                                                ASTType::kStruct_Kind));
+}
+
+/* structDeclaration varDeclarationEnd */
+std::unique_ptr<ASTVarDeclaration> Parser::structVarDeclaration(ASTModifiers modifiers) {
+    std::unique_ptr<ASTType> type = this->structDeclaration();
+    if (type == nullptr) {
+        return nullptr;
+    }
+    if (peek().fKind == Token::IDENTIFIER) {
+        Token name = this->nextToken();
+        std::unique_ptr<ASTVarDeclaration> result = this->varDeclarationEnd(modifiers, 
+                                                                            std::move(type), 
+                                                                            std::move(name.fText));
+        if (result != nullptr) {
+            for (size_t i = 0; i < result->fValues.size(); i++) {
+                if (result->fValues[i] != nullptr) {
+                    this->error(result->fValues[i]->fPosition, 
+                                "struct variables cannot be initialized");
+                }
+            }
+        }
+        return result;
+    }
+    this->expect(Token::SEMICOLON, "';'");
+    return nullptr;
+}
+
+/* (LBRACKET expression? RBRACKET)* (EQ expression)? (COMMA IDENTIFER 
+   (LBRACKET expression? RBRACKET)* (EQ expression)?)* SEMICOLON */
+std::unique_ptr<ASTVarDeclaration> Parser::varDeclarationEnd(ASTModifiers mods,
+                                                             std::unique_ptr<ASTType> type,
+                                                             std::string name) {
+    std::vector<std::string> names;
+    std::vector<std::vector<std::unique_ptr<ASTExpression>>> sizes;
+    names.push_back(name);
+    std::vector<std::unique_ptr<ASTExpression>> currentVarSizes;
+    while (this->peek().fKind == Token::LBRACKET) {
+        this->nextToken();
+        if (this->peek().fKind == Token::RBRACKET) {
+            this->nextToken();
+            currentVarSizes.push_back(nullptr);
+        } else {
+            std::unique_ptr<ASTExpression> size(this->expression());
+            if (!size) {
+                return nullptr;
+            }
+            currentVarSizes.push_back(std::move(size));
+            if (!this->expect(Token::RBRACKET, "']'")) {
+                return nullptr;
+            }
+        }
+    }
+    sizes.push_back(std::move(currentVarSizes));
+    std::vector<std::unique_ptr<ASTExpression>> values;
+    if (this->peek().fKind == Token::EQ) {
+        this->nextToken();
+        std::unique_ptr<ASTExpression> value(this->expression());
+        if (!value) {
+            return nullptr;
+        }
+        values.push_back(std::move(value));
+    } else {
+        values.push_back(nullptr);
+    }
+    while (this->peek().fKind == Token::COMMA) {
+        this->nextToken();
+        Token name;
+        if (!this->expect(Token::IDENTIFIER, "an identifier", &name)) {
+            return nullptr;
+        }
+        names.push_back(name.fText);
+        currentVarSizes.clear();
+        while (this->peek().fKind == Token::LBRACKET) {
+            this->nextToken();
+            if (this->peek().fKind == Token::RBRACKET) {
+                this->nextToken();
+                currentVarSizes.push_back(nullptr);
+            } else {
+                std::unique_ptr<ASTExpression> size(this->expression());
+                if (!size) {
+                    return nullptr;
+                }
+                currentVarSizes.push_back(std::move(size));
+                if (!this->expect(Token::RBRACKET, "']'")) {
+                    return nullptr;
+                }
+            }
+        }
+        sizes.push_back(std::move(currentVarSizes));
+        if (this->peek().fKind == Token::EQ) {
+            this->nextToken();
+            std::unique_ptr<ASTExpression> value(this->expression());
+            if (!value) {
+                return nullptr;
+            }
+            values.push_back(std::move(value));
+        } else {
+            values.push_back(nullptr);
+        }
+    }
+    if (!this->expect(Token::SEMICOLON, "';'")) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTVarDeclaration>(new ASTVarDeclaration(std::move(mods),
+                                                                    std::move(type),
+                                                                    std::move(names),
+                                                                    std::move(sizes),
+                                                                    std::move(values)));
+}
+
+/* modifiers type IDENTIFIER (LBRACKET INT_LITERAL RBRACKET)? */
+std::unique_ptr<ASTParameter> Parser::parameter() {
+    ASTModifiers modifiers = this->modifiers();
+    std::unique_ptr<ASTType> type = this->type();
+    if (!type) {
+        return nullptr;
+    }
+    Token name;
+    if (!this->expect(Token::IDENTIFIER, "an identifier", &name)) {
+        return nullptr;
+    }
+    std::vector<int> sizes;
+    while (this->peek().fKind == Token::LBRACKET) {
+        this->nextToken();
+        Token sizeToken;
+        if (!this->expect(Token::INT_LITERAL, "a positive integer", &sizeToken)) {
+            return nullptr;
+        }
+        sizes.push_back(SkSL::stoi(sizeToken.fText));
+        if (!this->expect(Token::RBRACKET, "']'")) {
+            return nullptr;
+        }
+    }
+    return std::unique_ptr<ASTParameter>(new ASTParameter(name.fPosition, modifiers, 
+                                                          std::move(type), name.fText, 
+                                                          std::move(sizes)));
+}
+
+/** (EQ INT_LITERAL)? */
+int Parser::layoutInt() {
+    if (!this->expect(Token::EQ, "'='")) {
+        return -1;
+    }
+    Token resultToken;
+    if (this->expect(Token::INT_LITERAL, "a non-negative integer", &resultToken)) {
+        return SkSL::stoi(resultToken.fText);
+    }
+    return -1;
+}
+
+/* LAYOUT LPAREN IDENTIFIER EQ INT_LITERAL (COMMA IDENTIFIER EQ INT_LITERAL)* 
+   RPAREN */
+ASTLayout Parser::layout() {
+    int location = -1;
+    int binding = -1;
+    int index = -1;
+    int set = -1;
+    int builtin = -1;
+    if (this->peek().fKind == Token::LAYOUT) {
+        this->nextToken();
+        if (!this->expect(Token::LPAREN, "'('")) {
+            return ASTLayout(location, binding, index, set, builtin);
+        }
+        for (;;) {
+            Token t = this->nextToken();
+            if (t.fText == "location") {
+                location = this->layoutInt();
+            } else if (t.fText == "binding") {
+                binding = this->layoutInt();
+            } else if (t.fText == "index") {
+                index = this->layoutInt();
+            } else if (t.fText == "set") {
+                set = this->layoutInt();
+            } else if (t.fText == "builtin") {
+                builtin = this->layoutInt();
+            } else {
+                this->error(t.fPosition, ("'" + t.fText + 
+                                          "' is not a valid layout qualifier").c_str());
+            }
+            if (this->peek().fKind == Token::RPAREN) {
+                this->nextToken();
+                break;
+            }
+            if (!this->expect(Token::COMMA, "','")) {
+                break;
+            }
+        }
+    }
+    return ASTLayout(location, binding, index, set, builtin);
+}
+
+/* layout? (UNIFORM | CONST | IN | OUT | INOUT | LOWP | 
+   MEDIUMP | HIGHP)* */
+ASTModifiers Parser::modifiers() {
+    ASTLayout layout = this->layout();
+    int flags = 0;
+    for (;;) {
+        // TODO: handle duplicate / incompatible flags
+        switch (peek().fKind) {
+            case Token::UNIFORM:
+                this->nextToken();
+                flags |= ASTModifiers::kUniform_Flag;
+                break;
+            case Token::CONST:
+                this->nextToken();
+                flags |= ASTModifiers::kConst_Flag;
+                break;
+            case Token::IN:
+                this->nextToken();
+                flags |= ASTModifiers::kIn_Flag;
+                break;
+            case Token::OUT:
+                this->nextToken();
+                flags |= ASTModifiers::kOut_Flag;
+                break;
+            case Token::INOUT:
+                this->nextToken();
+                flags |= ASTModifiers::kIn_Flag;
+                flags |= ASTModifiers::kOut_Flag;
+                break;
+            case Token::LOWP:
+                this->nextToken();
+                flags |= ASTModifiers::kLowp_Flag;
+                break;
+            case Token::MEDIUMP:
+                this->nextToken();
+                flags |= ASTModifiers::kMediump_Flag;
+                break;
+            case Token::HIGHP:
+                this->nextToken();
+                flags |= ASTModifiers::kHighp_Flag;
+                break;
+            default:
+                return ASTModifiers(layout, flags);
+        }
+    }
+}
+
+/* ifStatement | forStatement | doStatement | whileStatement | block | expression */
+std::unique_ptr<ASTStatement> Parser::statement() {
+    Token start = this->peek();
+    switch (start.fKind) {
+        case Token::IF:
+            return this->ifStatement();
+        case Token::FOR:
+            return this->forStatement();
+        case Token::DO:
+            return this->doStatement();
+        case Token::WHILE:
+            return this->whileStatement();
+        case Token::RETURN:
+            return this->returnStatement();
+        case Token::BREAK:
+            return this->breakStatement();
+        case Token::CONTINUE:
+            return this->continueStatement();
+        case Token::DISCARD:
+            return this->discardStatement();
+        case Token::LBRACE:
+            return this->block();
+        case Token::SEMICOLON:
+            this->nextToken(); 
+            return std::unique_ptr<ASTStatement>(new ASTBlock(start.fPosition, {}));
+        case Token::CONST:   // fall through
+        case Token::HIGHP:   // fall through
+        case Token::MEDIUMP: // fall through
+        case Token::LOWP: {
+            auto decl = this->varDeclaration();
+            if (decl == nullptr) {
+                return nullptr;
+            }
+            return std::unique_ptr<ASTStatement>(new ASTVarDeclarationStatement(std::move(decl)));
+        }
+        case Token::IDENTIFIER:
+            if (this->isType(start.fText)) {
+                auto decl = this->varDeclaration();
+                if (decl == nullptr) {
+                    return nullptr;
+                }
+                return std::unique_ptr<ASTStatement>(new ASTVarDeclarationStatement(
+                                                                                  std::move(decl)));
+            }
+            // fall through
+        default:
+            return this->expressionStatement();
+    }    
+}
+
+/* IDENTIFIER(type) */
+std::unique_ptr<ASTType> Parser::type() {
+    Token type;
+    if (!this->expect(Token::IDENTIFIER, "a type", &type)) {
+        return nullptr;
+    }
+    if (!this->isType(type.fText)) {
+        this->error(type.fPosition, ("no type named '" + type.fText + "'").c_str());
+        return nullptr;
+    }
+    return std::unique_ptr<ASTType>(new ASTType(type.fPosition, std::move(type.fText), 
+                                                ASTType::kIdentifier_Kind));
+}
+
+/* IDENTIFIER LBRACE varDeclaration* RBRACE */
+std::unique_ptr<ASTDeclaration> Parser::interfaceBlock(ASTModifiers mods) {
+    Token name;
+    if (!this->expect(Token::IDENTIFIER, "an identifier", &name)) {
+        return nullptr;
+    }
+    if (peek().fKind != Token::LBRACE) {
+        // we only get into interfaceBlock if we found a top-level identifier which was not a type.
+        // 99% of the time, the user was not actually intending to create an interface block, so 
+        // it's better to report it as an unknown type
+        this->error(name.fPosition, "no type named '" + name.fText + "'");
+        return nullptr;
+    }
+    this->nextToken();
+    std::vector<std::unique_ptr<ASTVarDeclaration>> decls; 
+    while (this->peek().fKind != Token::RBRACE) {
+        std::unique_ptr<ASTVarDeclaration> decl = this->varDeclaration();
+        if (decl == nullptr) {
+            return nullptr;
+        }
+        decls.push_back(std::move(decl));
+    }
+    this->nextToken();
+    std::string valueName;
+    if (this->peek().fKind == Token::IDENTIFIER) {
+        valueName = this->nextToken().fText;
+    }
+    this->expect(Token::SEMICOLON, "';'");
+    return std::unique_ptr<ASTDeclaration>(new ASTInterfaceBlock(name.fPosition, mods, 
+                                                                 name.fText, std::move(valueName),
+                                                                 std::move(decls)));
+}
+
+/* IF LPAREN expression RPAREN statement (ELSE statement)? */
+std::unique_ptr<ASTIfStatement> Parser::ifStatement() {
+    Token start;
+    if (!this->expect(Token::IF, "'if'", &start)) {
+        return nullptr;
+    }
+    if (!this->expect(Token::LPAREN, "'('")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTExpression> test(this->expression());
+    if (test == nullptr) {
+        return nullptr;
+    }
+    if (!this->expect(Token::RPAREN, "')'")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTStatement> ifTrue(this->statement());
+    if (ifTrue == nullptr) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTStatement> ifFalse;
+    if (this->peek().fKind == Token::ELSE) {
+        this->nextToken();
+        ifFalse = this->statement();
+        if (!ifFalse) {
+            return nullptr;
+        }
+    }
+    return std::unique_ptr<ASTIfStatement>(new ASTIfStatement(start.fPosition, std::move(test), 
+                                                              std::move(ifTrue), 
+                                                              std::move(ifFalse)));
+}
+
+/* DO statement WHILE LPAREN expression RPAREN SEMICOLON */
+std::unique_ptr<ASTDoStatement> Parser::doStatement() {
+    Token start;
+    if (!this->expect(Token::DO, "'do'", &start)) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTStatement> statement(this->statement());
+    if (statement == nullptr) {
+        return nullptr;
+    }
+    if (!this->expect(Token::WHILE, "'while'")) {
+        return nullptr;
+    }
+    if (!this->expect(Token::LPAREN, "'('")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTExpression> test(this->expression());
+    if (test == nullptr) {
+        return nullptr;
+    }
+    if (!this->expect(Token::RPAREN, "')'")) {
+        return nullptr;
+    }
+    if (!this->expect(Token::SEMICOLON, "';'")) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTDoStatement>(new ASTDoStatement(start.fPosition, 
+                                                              std::move(statement),
+                                                              std::move(test)));
+}
+
+/* WHILE LPAREN expression RPAREN STATEMENT */
+std::unique_ptr<ASTWhileStatement> Parser::whileStatement() {
+    Token start;
+    if (!this->expect(Token::WHILE, "'while'", &start)) {
+        return nullptr;
+    }
+    if (!this->expect(Token::LPAREN, "'('")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTExpression> test(this->expression());
+    if (test == nullptr) {
+        return nullptr;
+    }
+    if (!this->expect(Token::RPAREN, "')'")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTStatement> statement(this->statement());
+    if (statement == nullptr) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTWhileStatement>(new ASTWhileStatement(start.fPosition, 
+                                                                    std::move(test), 
+                                                                    std::move(statement)));
+}
+
+/* FOR LPAREN (declaration | expression)? SEMICOLON expression? SEMICOLON expression? RPAREN 
+   STATEMENT */
+std::unique_ptr<ASTForStatement> Parser::forStatement() {
+    Token start;
+    if (!this->expect(Token::FOR, "'for'", &start)) {
+        return nullptr;
+    }
+    if (!this->expect(Token::LPAREN, "'('")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTStatement> initializer;
+    Token nextToken = this->peek();
+    switch (nextToken.fKind) {
+        case Token::SEMICOLON: 
+            break;
+        case Token::CONST:
+            initializer = std::unique_ptr<ASTStatement>(new ASTVarDeclarationStatement(
+                                                                           this->varDeclaration()));
+            break;
+        case Token::IDENTIFIER: 
+            if (this->isType(nextToken.fText)) {
+                initializer = std::unique_ptr<ASTStatement>(new ASTVarDeclarationStatement(
+                                                                           this->varDeclaration()));
+                break;
+            }
+            // fall through
+        default:
+            initializer = this->expressionStatement();
+    }
+    std::unique_ptr<ASTExpression> test;
+    if (this->peek().fKind != Token::SEMICOLON) {
+        test = this->expression();
+        if (!test) {
+            return nullptr;
+        }
+    }
+    if (!this->expect(Token::SEMICOLON, "';'")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTExpression> next;
+    if (this->peek().fKind != Token::SEMICOLON) {
+        next = this->expression();
+        if (!next) {
+            return nullptr;
+        }
+    }
+    if (!this->expect(Token::RPAREN, "')'")) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTStatement> statement(this->statement());
+    if (statement == nullptr) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTForStatement>(new ASTForStatement(start.fPosition, 
+                                                                std::move(initializer),
+                                                                std::move(test), std::move(next),
+                                                                std::move(statement)));
+}
+
+/* RETURN expression? SEMICOLON */
+std::unique_ptr<ASTReturnStatement> Parser::returnStatement() {
+    Token start;
+    if (!this->expect(Token::RETURN, "'return'", &start)) {
+        return nullptr;
+    }
+    std::unique_ptr<ASTExpression> expression;
+    if (this->peek().fKind != Token::SEMICOLON) {
+        expression = this->expression();
+        if (!expression) {
+            return nullptr;
+        }
+    }
+    if (!this->expect(Token::SEMICOLON, "';'")) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTReturnStatement>(new ASTReturnStatement(start.fPosition, 
+                                                                      std::move(expression)));
+}
+
+/* BREAK SEMICOLON */
+std::unique_ptr<ASTBreakStatement> Parser::breakStatement() {
+    Token start;
+    if (!this->expect(Token::BREAK, "'break'", &start)) {
+        return nullptr;
+    }
+    if (!this->expect(Token::SEMICOLON, "';'")) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTBreakStatement>(new ASTBreakStatement(start.fPosition));
+}
+
+/* CONTINUE SEMICOLON */
+std::unique_ptr<ASTContinueStatement> Parser::continueStatement() {
+    Token start;
+    if (!this->expect(Token::CONTINUE, "'continue'", &start)) {
+        return nullptr;
+    }
+    if (!this->expect(Token::SEMICOLON, "';'")) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTContinueStatement>(new ASTContinueStatement(start.fPosition));
+}
+
+/* DISCARD SEMICOLON */
+std::unique_ptr<ASTDiscardStatement> Parser::discardStatement() {
+    Token start;
+    if (!this->expect(Token::DISCARD, "'continue'", &start)) {
+        return nullptr;
+    }
+    if (!this->expect(Token::SEMICOLON, "';'")) {
+        return nullptr;
+    }
+    return std::unique_ptr<ASTDiscardStatement>(new ASTDiscardStatement(start.fPosition));
+}
+
+/* LBRACE statement* RBRACE */
+std::unique_ptr<ASTBlock> Parser::block() {
+    Token start;
+    if (!this->expect(Token::LBRACE, "'{'", &start)) {
+        return nullptr;
+    }
+    std::vector<std::unique_ptr<ASTStatement>> statements;
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::RBRACE: 
+                this->nextToken();
+                return std::unique_ptr<ASTBlock>(new ASTBlock(start.fPosition, 
+                                                              std::move(statements)));
+            case Token::END_OF_FILE: 
+                this->error(this->peek().fPosition, "expected '}', but found end of file");
+                return nullptr;
+            default: {
+                std::unique_ptr<ASTStatement> statement = this->statement();
+                if (statement == nullptr) {
+                    return nullptr;
+                }
+                statements.push_back(std::move(statement));
+            }
+        }
+    }
+}
+
+/* expression SEMICOLON */
+std::unique_ptr<ASTExpressionStatement> Parser::expressionStatement() {
+    std::unique_ptr<ASTExpression> expr = this->expression();
+    if (expr) {
+        if (this->expect(Token::SEMICOLON, "';'")) {
+            ASTExpressionStatement* result = new ASTExpressionStatement(std::move(expr));
+            return std::unique_ptr<ASTExpressionStatement>(result);
+        }
+    }
+    return nullptr;
+}
+
+/* assignmentExpression */
+std::unique_ptr<ASTExpression> Parser::expression() {
+    return this->assignmentExpression();
+}
+
+/* ternaryExpression ((EQEQ | STAREQ | SLASHEQ | PERCENTEQ | PLUSEQ | MINUSEQ | SHLEQ | SHREQ |
+   BITWISEANDEQ | BITWISEXOREQ | BITWISEOREQ | LOGICALANDEQ | LOGICALXOREQ | LOGICALOREQ)
+   assignmentExpression)*
+ */
+std::unique_ptr<ASTExpression> Parser::assignmentExpression() {
+    std::unique_ptr<ASTExpression> result = this->ternaryExpression();
+    if (!result) {
+        return nullptr;
+    }
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::EQ:           // fall through
+            case Token::STAREQ:       // fall through
+            case Token::SLASHEQ:      // fall through
+            case Token::PERCENTEQ:    // fall through
+            case Token::PLUSEQ:       // fall through
+            case Token::MINUSEQ:      // fall through
+            case Token::SHLEQ:        // fall through
+            case Token::SHREQ:        // fall through
+            case Token::BITWISEANDEQ: // fall through
+            case Token::BITWISEXOREQ: // fall through
+            case Token::BITWISEOREQ:  // fall through
+            case Token::LOGICALANDEQ: // fall through
+            case Token::LOGICALXOREQ: // fall through
+            case Token::LOGICALOREQ: {
+                Token t = this->nextToken();
+                std::unique_ptr<ASTExpression> right = this->assignmentExpression();
+                if (right == nullptr) {
+                    return nullptr;
+                }
+                result = std::unique_ptr<ASTExpression>(new ASTBinaryExpression(std::move(result), 
+                                                                                t, 
+                                                                                std::move(right)));
+            }
+            default:
+                return result;
+        }
+    }
+}
+
+/* logicalOrExpression ('?' expression ':' assignmentExpression)? */
+std::unique_ptr<ASTExpression> Parser::ternaryExpression() {
+    std::unique_ptr<ASTExpression> result = this->logicalOrExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    if (this->peek().fKind == Token::QUESTION) {
+        Token question = this->nextToken();
+        std::unique_ptr<ASTExpression> trueExpr = this->expression();
+        if (trueExpr == nullptr) {
+            return nullptr;
+        }
+        if (this->expect(Token::COLON, "':'")) {
+            std::unique_ptr<ASTExpression> falseExpr = this->assignmentExpression();
+            return std::unique_ptr<ASTExpression>(new ASTTernaryExpression(std::move(result), 
+                                                                           std::move(trueExpr), 
+                                                                           std::move(falseExpr)));
+        }
+        return nullptr;
+    }
+    return result;
+}
+
+/* logicalXorExpression (LOGICALOR logicalXorExpression)* */
+std::unique_ptr<ASTExpression> Parser::logicalOrExpression() {
+    std::unique_ptr<ASTExpression> result = this->logicalXorExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    while (this->peek().fKind == Token::LOGICALOR) {
+        Token t = this->nextToken();
+        std::unique_ptr<ASTExpression> right = this->logicalXorExpression();
+        if (right == nullptr) {
+            return nullptr;
+        }
+        result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+    }
+    return result;
+}
+
+/* logicalAndExpression (LOGICALXOR logicalAndExpression)* */
+std::unique_ptr<ASTExpression> Parser::logicalXorExpression() {
+    std::unique_ptr<ASTExpression> result = this->logicalAndExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    while (this->peek().fKind == Token::LOGICALXOR) {
+        Token t = this->nextToken();
+        std::unique_ptr<ASTExpression> right = this->logicalAndExpression();
+        if (right == nullptr) {
+            return nullptr;
+        }
+        result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+    }
+    return result;
+}
+
+/* bitwiseOrExpression (LOGICALAND bitwiseOrExpression)* */
+std::unique_ptr<ASTExpression> Parser::logicalAndExpression() {
+    std::unique_ptr<ASTExpression> result = this->bitwiseOrExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    while (this->peek().fKind == Token::LOGICALAND) {
+        Token t = this->nextToken();
+        std::unique_ptr<ASTExpression> right = this->bitwiseOrExpression();
+        if (right == nullptr) {
+            return nullptr;
+        }
+        result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+    }
+    return result;
+}
+
+/* bitwiseXorExpression (BITWISEOR bitwiseXorExpression)* */
+std::unique_ptr<ASTExpression> Parser::bitwiseOrExpression() {
+    std::unique_ptr<ASTExpression> result = this->bitwiseXorExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    while (this->peek().fKind == Token::BITWISEOR) {
+        Token t = this->nextToken();
+        std::unique_ptr<ASTExpression> right = this->bitwiseXorExpression();
+        if (right == nullptr) {
+            return nullptr;
+        }
+        result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+    }
+    return result;
+}
+
+/* bitwiseAndExpression (BITWISEXOR bitwiseAndExpression)* */
+std::unique_ptr<ASTExpression> Parser::bitwiseXorExpression() {
+    std::unique_ptr<ASTExpression> result = this->bitwiseAndExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    while (this->peek().fKind == Token::BITWISEXOR) {
+        Token t = this->nextToken();
+        std::unique_ptr<ASTExpression> right = this->bitwiseAndExpression();
+        if (right == nullptr) {
+            return nullptr;
+        }
+        result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+    }
+    return result;
+}
+
+/* equalityExpression (BITWISEAND equalityExpression)* */
+std::unique_ptr<ASTExpression> Parser::bitwiseAndExpression() {
+    std::unique_ptr<ASTExpression> result = this->equalityExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    while (this->peek().fKind == Token::BITWISEAND) {
+        Token t = this->nextToken();
+        std::unique_ptr<ASTExpression> right = this->equalityExpression();
+        if (right == nullptr) {
+            return nullptr;
+        }
+        result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+    }
+    return result;
+}
+
+/* relationalExpression ((EQEQ | NEQ) relationalExpression)* */
+std::unique_ptr<ASTExpression> Parser::equalityExpression() {
+    std::unique_ptr<ASTExpression> result = this->relationalExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::EQEQ:   // fall through
+            case Token::NEQ: {
+                Token t = this->nextToken();
+                std::unique_ptr<ASTExpression> right = this->relationalExpression();
+                if (right == nullptr) {
+                    return nullptr;
+                }
+                result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+                break;
+            }
+            default:
+                return result;
+        }
+    }
+}
+
+/* shiftExpression ((LT | GT | LTEQ | GTEQ) shiftExpression)* */
+std::unique_ptr<ASTExpression> Parser::relationalExpression() {
+    std::unique_ptr<ASTExpression> result = this->shiftExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::LT:   // fall through
+            case Token::GT:   // fall through
+            case Token::LTEQ: // fall through
+            case Token::GTEQ: {
+                Token t = this->nextToken();
+                std::unique_ptr<ASTExpression> right = this->shiftExpression();
+                if (right == nullptr) {
+                    return nullptr;
+                }
+                result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+                break;
+            }
+            default:
+                return result;
+        }
+    }
+}
+
+/* additiveExpression ((SHL | SHR) additiveExpression)* */
+std::unique_ptr<ASTExpression> Parser::shiftExpression() {
+    std::unique_ptr<ASTExpression> result = this->additiveExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::SHL: // fall through
+            case Token::SHR: {
+                Token t = this->nextToken();
+                std::unique_ptr<ASTExpression> right = this->additiveExpression();
+                if (right == nullptr) {
+                    return nullptr;
+                }
+                result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+                break;
+            }
+            default:
+                return result;
+        }
+    }
+}
+
+/* multiplicativeExpression ((PLUS | MINUS) multiplicativeExpression)* */
+std::unique_ptr<ASTExpression> Parser::additiveExpression() {
+    std::unique_ptr<ASTExpression> result = this->multiplicativeExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::PLUS: // fall through
+            case Token::MINUS: {
+                Token t = this->nextToken();
+                std::unique_ptr<ASTExpression> right = this->multiplicativeExpression();
+                if (right == nullptr) {
+                    return nullptr;
+                }
+                result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+                break;
+            }
+            default:
+                return result;
+        }
+    }
+}
+
+/* unaryExpression ((STAR | SLASH | PERCENT) unaryExpression)* */
+std::unique_ptr<ASTExpression> Parser::multiplicativeExpression() {
+    std::unique_ptr<ASTExpression> result = this->unaryExpression();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::STAR: // fall through
+            case Token::SLASH: // fall through
+            case Token::PERCENT: {
+                Token t = this->nextToken();
+                std::unique_ptr<ASTExpression> right = this->unaryExpression();
+                if (right == nullptr) {
+                    return nullptr;
+                }
+                result.reset(new ASTBinaryExpression(std::move(result), t, std::move(right)));
+                break;
+            }
+            default:
+                return result;
+        }
+    }
+}
+
+/* postfixExpression | (PLUS | MINUS | NOT | PLUSPLUS | MINUSMINUS) unaryExpression */
+std::unique_ptr<ASTExpression> Parser::unaryExpression() {
+    switch (this->peek().fKind) {
+        case Token::PLUS:     // fall through
+        case Token::MINUS:    // fall through
+        case Token::NOT:      // fall through
+        case Token::PLUSPLUS: // fall through
+        case Token::MINUSMINUS: {
+            Token t = this->nextToken();
+            std::unique_ptr<ASTExpression> expr = this->unaryExpression();
+            if (expr == nullptr) {
+                return nullptr;
+            }
+            return std::unique_ptr<ASTExpression>(new ASTPrefixExpression(t, std::move(expr)));
+        }
+        default:
+            return this->postfixExpression();
+    }
+}
+
+/* term suffix* */
+std::unique_ptr<ASTExpression> Parser::postfixExpression() {
+    std::unique_ptr<ASTExpression> result = this->term();
+    if (result == nullptr) {
+        return nullptr;
+    }
+    for (;;) {
+        switch (this->peek().fKind) {
+            case Token::LBRACKET: // fall through
+            case Token::DOT:      // fall through
+            case Token::LPAREN:   // fall through
+            case Token::PLUSPLUS: // fall through
+            case Token::MINUSMINUS: {
+                std::unique_ptr<ASTSuffix> s = this->suffix();
+                if (s == nullptr) {
+                    return nullptr;
+                }
+                result.reset(new ASTSuffixExpression(std::move(result), std::move(s)));
+                break;
+            }
+            default:
+                return result;
+        }
+    }
+}
+
+/* LBRACKET expression RBRACKET | DOT IDENTIFIER | LPAREN parameters RPAREN | 
+   PLUSPLUS | MINUSMINUS */
+std::unique_ptr<ASTSuffix> Parser::suffix() {
+    Token next = this->nextToken();
+    switch (next.fKind) {
+        case Token::LBRACKET: {
+            std::unique_ptr<ASTExpression> e = this->expression();
+            if (e == nullptr) {
+                return nullptr;
+            }
+            this->expect(Token::RBRACKET, "']' to complete array access expression");
+            return std::unique_ptr<ASTSuffix>(new ASTIndexSuffix(std::move(e)));
+        }
+        case Token::DOT: {
+            Position pos = this->peek().fPosition;
+            std::string text;
+            if (this->identifier(&text)) {
+                return std::unique_ptr<ASTSuffix>(new ASTFieldSuffix(pos, std::move(text)));
+            }
+            return nullptr;
+        }
+        case Token::LPAREN: {
+            std::vector<std::unique_ptr<ASTExpression>> parameters;
+            if (this->peek().fKind != Token::RPAREN) {
+                for (;;) {
+                    std::unique_ptr<ASTExpression> expr = this->expression();
+                    if (expr == nullptr) {
+                        return nullptr;
+                    }
+                    parameters.push_back(std::move(expr));
+                    if (this->peek().fKind != Token::COMMA) {
+                        break;
+                    }
+                    this->nextToken();
+                }
+            }
+            this->expect(Token::RPAREN, "')' to complete function parameters");
+            return std::unique_ptr<ASTSuffix>(new ASTCallSuffix(next.fPosition, 
+                                                                std::move(parameters)));
+        }
+        case Token::PLUSPLUS:
+            return std::unique_ptr<ASTSuffix>(new ASTSuffix(next.fPosition, 
+                                                            ASTSuffix::kPostIncrement_Kind));
+        case Token::MINUSMINUS:
+            return std::unique_ptr<ASTSuffix>(new ASTSuffix(next.fPosition,
+                                                            ASTSuffix::kPostDecrement_Kind));
+        default: {
+            this->error(next.fPosition,  "expected expression suffix, but found '" + next.fText + 
+                                         "'\n");
+            return nullptr;
+        }
+    }
+}
+
+/* IDENTIFIER | intLiteral | floatLiteral | boolLiteral | '(' expression ')' */
+std::unique_ptr<ASTExpression> Parser::term() {
+    std::unique_ptr<ASTExpression> result;
+    Token t = this->peek();
+    switch (t.fKind) {
+        case Token::IDENTIFIER: {
+            std::string text;
+            if (this->identifier(&text)) {
+                result.reset(new ASTIdentifier(t.fPosition, std::move(text)));
+            }
+            break;
+        }
+        case Token::INT_LITERAL: {
+            int64_t i;
+            if (this->intLiteral(&i)) {
+                result.reset(new ASTIntLiteral(t.fPosition, i));
+            }
+            break;
+        }
+        case Token::FLOAT_LITERAL: {
+            double f;
+            if (this->floatLiteral(&f)) {
+                result.reset(new ASTFloatLiteral(t.fPosition, f));
+            }
+            break;
+        }
+        case Token::TRUE_LITERAL: // fall through
+        case Token::FALSE_LITERAL: {
+            bool b;
+            if (this->boolLiteral(&b)) {
+                result.reset(new ASTBoolLiteral(t.fPosition, b));
+            }
+            break;
+        }
+        case Token::LPAREN: {
+            this->nextToken();
+            result = this->expression();
+            if (result) {
+                this->expect(Token::RPAREN, "')' to complete expression");
+            }
+            break;
+        }
+        default:
+            this->nextToken();
+            this->error(t.fPosition,  "expected expression, but found '" + t.fText + "'\n");
+            result = nullptr;
+    }
+    return result;
+}
+
+/* INT_LITERAL */
+bool Parser::intLiteral(int64_t* dest) {
+    Token t;
+    if (this->expect(Token::INT_LITERAL, "integer literal", &t)) {
+        *dest = SkSL::stol(t.fText);
+        return true;
+    }
+    return false;
+}
+
+/* FLOAT_LITERAL */
+bool Parser::floatLiteral(double* dest) {
+    Token t;
+    if (this->expect(Token::FLOAT_LITERAL, "float literal", &t)) {
+        *dest = SkSL::stod(t.fText);
+        return true;
+    }
+    return false;
+}
+
+/* TRUE_LITERAL | FALSE_LITERAL */
+bool Parser::boolLiteral(bool* dest) {
+    Token t = this->nextToken();
+    switch (t.fKind) {
+        case Token::TRUE_LITERAL:
+            *dest = true;
+            return true;
+        case Token::FALSE_LITERAL:
+            *dest = false;
+            return true;
+        default:
+            this->error(t.fPosition, "expected 'true' or 'false', but found '" + t.fText + "'\n");
+            return false;
+    }
+}
+
+/* IDENTIFIER */
+bool Parser::identifier(std::string* dest) {
+    Token t;
+    if (this->expect(Token::IDENTIFIER, "identifier", &t)) {
+        *dest = t.fText; 
+        return true;
+    }
+    return false;
+}
+
+} // namespace