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Flag non-nullable values with call expressions in if statements as errors

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This commit is contained in:
Justin Bay
2019-08-10 13:50:14 -04:00
parent 79bcb3d547
commit 006a327320
7 changed files with 440 additions and 2 deletions
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20
src/compiler/checker.ts
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@@ -27930,7 +27930,25 @@ namespace ts {
// Grammar checking
checkGrammarStatementInAmbientContext(node);
checkTruthinessExpression(node.expression);
const type = checkTruthinessExpression(node.expression);
if (strictNullChecks &&
(node.expression.kind === SyntaxKind.Identifier ||
node.expression.kind === SyntaxKind.PropertyAccessExpression ||
node.expression.kind === SyntaxKind.ElementAccessExpression)) {
const possiblyFalsy = !!getFalsyFlags(type);
if (!possiblyFalsy) {
// While it technically should be invalid for any known-truthy value
// to be tested, we de-scope to functions as a heuristic to identify
// the most common bugs. There are too many false positives for values
// sourced from type definitions without strictNullChecks otherwise.
const callSignatures = getSignaturesOfType(type, SignatureKind.Call);
if (callSignatures.length > 0) {
error(node.expression, Diagnostics.This_condition_will_always_return_true_since_the_function_is_always_defined_Did_you_mean_to_call_it_instead);
}
}
}
checkSourceElement(node.thenStatement);
if (node.thenStatement.kind === SyntaxKind.EmptyStatement) {

5
src/compiler/diagnosticMessages.json
View File

@@ -2689,7 +2689,10 @@
"category": "Error",
"code": 2773
},
"This condition will always return true since the function is always defined. Did you mean to call it instead?": {
"category": "Error",
"code": 2774
},
"Import declaration '{0}' is using private name '{1}'.": {
"category": "Error",
"code": 4000