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asm-llvm: Improve error messages for undefined identifiers.
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We don't technically know whether an unknown identifier is actually
a forward reference to a future function or function table.  But we
emit better error messages if we do a specific check in places where
a function or function table isn't valid instead of waiting for the
typecheck to fail.
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@cscott
cscott committed Jun 6, 2013
1 parent cf17be7 commit 31ec52d
Showing 1 changed file with 42 additions and 18 deletions.
60 changes: 42 additions & 18 deletions asm-llvm.js
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Expand Up @@ -224,6 +224,8 @@ define([], function asm_llvm() {
// identifiers.
Types.Module = Type.derive("Module");
// Special type used to mark possible forward references.
// Note that a value of ForwardReference type should always be actually
// of type `Arrow` (local function) or `Table` (global function table).
Types.ForwardReference = Type.derive("ForwardReference");

// Utility functions.
Expand Down Expand Up @@ -1688,6 +1690,19 @@ define([], function asm_llvm() {
"should be " + (should ? should.toString() : '?') +
", but was " + (actual ? actual.toString() : '?'));
};
// Raise with a nice error message if the given binding is
// a forward reference. Since `ForwardReference` is only used
// in narrow circumstances when parsing a call to a local function
// or dereference of a function table, we can get better error
// messages by aggressively asserting that a given binding should
// not be a forward reference.
var defcheck = function(binding, message) {
if (binding.type !== Types.ForwardReference) { return binding; }
raise(binding.pos || tokStart,
(binding.id ? ("'"+binding.id+"' is ") : "") +"undefined,"+
" or an invalid reference to future function or function"+
" table" + (message ? (" ("+message+")") : ""));
};

// Merge types. This is used for single-forward-pass compilation:
// when we first see a reference to a function (or its return type)
Expand Down Expand Up @@ -1798,6 +1813,7 @@ define([], function asm_llvm() {
binding = GlobalBinding.New(Types.ForwardReference, false);
binding.pending = true;
binding.id = id; // for better error messages
binding.pos = lastStart; // ditto
module.env.bind(id, binding, lastStart);
}
return binding;
Expand All @@ -1823,6 +1839,7 @@ define([], function asm_llvm() {
// This will be a MemberExpression (or a CallExpression
// through function table).
if (base.type.arrayBufferView) {
defcheck(property);
// `MemberExpression := x:Identifier[n:NumericLiteral]`
if (ConstantBinding.hasInstance(property)) {
if (property.type !== Types.Fixnum &&
Expand Down Expand Up @@ -1867,26 +1884,29 @@ define([], function asm_llvm() {
expect(_bracketR);
return parseSubscripts(base, plusCoerced);
} else if (eat(_parenL)) {
/* XXX handle base=ForwardRef */
var startPos = lastStart;
var callArguments = parseExprList(_parenR, false);
// type-check
var binding;
if (base.type===Types.Function) {
callArguments.forEach(function(b, i) {
typecheck(b.type, Types.Extern,
"argument "+i+" to foreign function",
startPos);
var msg = "argument "+i+" to foreign function";
defcheck(b, msg);
typecheck(b.type, Types.Extern, msg, startPos);
});
binding = TempBinding.New(Types.Unknown);
} else if (base.type.arrow || base.type.functiontypes) {
var ty = base.type.apply(
callArguments.map(function(b){ return b.type; }));
callArguments.map(function(b){
return defcheck(b).type;
}));
if (ty===null) {
raise(startPos, "call argument mismatch; wants "+
base.type.toString());
}
binding = TempBinding.New(ty);
} else if (base.type === Types.ForwardReference) {
raise(startPos, "references to future functions not implemented");
} else {
raise(startPos, "bad call expression");
}
Expand All @@ -1912,7 +1932,7 @@ define([], function asm_llvm() {
}
console.assert(!update);
next();
var argument = parseMaybeUnary(operator==='+');
var argument = defcheck(parseMaybeUnary(operator==='+'));
// Special case the negation of a constant.
if (ConstantBinding.hasInstance(argument) && operator==='-') {
return argument.negate();
Expand Down Expand Up @@ -1955,6 +1975,7 @@ define([], function asm_llvm() {
}
next();
var right = parseExprOp(parseMaybeUnary(false), prec);
defcheck(left); defcheck(right);
ty = ty.apply([left.type, right.type]);
if (ty===null && (operator==='+' || operator==='-')) {
/* Special validation for "AdditiveExpression" */
Expand Down Expand Up @@ -2024,7 +2045,7 @@ define([], function asm_llvm() {
var expr = parseExprOps();
var startPos = tokStart;
if (eat(_question)) {
var test = expr;
var test = defcheck(expr);
typecheck(test.type, Types.Int, "conditional test", startPos);
var consequent = parseExpression(true);
expect(_colon);
Expand Down Expand Up @@ -2067,11 +2088,12 @@ define([], function asm_llvm() {
typecheck(right.type, left.type, "rhs of assignment",
startPos);
} else if (GlobalBinding.hasInstance(left)) {
typecheck(right.type, left.type, "rhs of assignment",
startPos);
if (!left.mutable) {
raise(startPos, "not mutable");
raise(startPos, (left.id ? "'"+left.id+"' ":"") +
"not mutable or undefined");
}
typecheck(right.type, left.type, "rhs of assignment",
startPos);
// Now check `lhs:MemberExpression = rhs:AssignmentExpression`.
} else if (ViewBinding.hasInstance(left)) {
typecheck(right.type, left.type, "rhs of assignment",
Expand Down Expand Up @@ -2161,7 +2183,7 @@ define([], function asm_llvm() {
// Parse a while loop.
next();
startPos = tokStart;
var whileTest = parseParenExpression();
var whileTest = defcheck(parseParenExpression());
typecheck(whileTest.type, Types.Int, "while loop condition",
startPos);
module.func.labels.push(loopLabel);
Expand All @@ -2177,7 +2199,7 @@ define([], function asm_llvm() {
module.func.labels.pop();
expect(_while);
startPos = tokStart;
var doTest = parseParenExpression();
var doTest = defcheck(parseParenExpression());
semicolon();
typecheck(doTest.type, Types.Int, "do-while loop condition",
startPos);
Expand All @@ -2194,14 +2216,14 @@ define([], function asm_llvm() {
module.func.labels.push(loopLabel);
expect(_parenL);
if (tokType === _semi) { return parseFor(null); }
var init = parseExpression(false);
var init = defcheck(parseExpression(false));
return parseFor(init);

// #### IfStatement
} else if (starttype===_if) {
next();
startPos = tokStart;
var ifTest = parseParenExpression();
var ifTest = defcheck(parseParenExpression());
typecheck(ifTest.type, Types.Int, "if statement condition",
startPos);
var consequent = parseStatement();
Expand All @@ -2221,7 +2243,7 @@ define([], function asm_llvm() {
if (eat(_semi) || canInsertSemicolon()) {
ty = Types.Void;
} else {
var binding = parseExpression(); semicolon();
var binding = defcheck(parseExpression()); semicolon();
ty = binding.type;
}
module.func.retType =
Expand All @@ -2232,7 +2254,7 @@ define([], function asm_llvm() {
} else if (starttype===_switch) {
next();
startPos = tokStart;
var switchTest = parseParenExpression();
var switchTest = defcheck(parseParenExpression());
typecheck(switchTest, Types.Signed, "switch discriminant",
startPos);
var cases = [];
Expand Down Expand Up @@ -2337,12 +2359,14 @@ define([], function asm_llvm() {
parseFor = function(init) {
expect(_semi);
var startPos = tokStart;
var test = (tokType === _semi) ? null : parseExpression();
var test = (tokType === _semi) ? null :
defcheck(parseExpression());
if (test!==null) {
typecheck(test.type, Types.Int, "for-loop condition", startPos);
}
expect(_semi);
var update = (tokType === _parenR) ? null : parseExpression();
var update = (tokType === _parenR) ? null :
defcheck(parseExpression());
expect(_parenR);
var body = parseStatement();
module.func.labels.pop();
Expand Down

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