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Add strict-type-predicates rule
#2046
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ajafff
reviewed
Jan 16, 2017
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [F] | ||
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| get<number | undefined>() === undefined; | ||
| get<string | undefined>() == null; |
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Could this rule also check for non strict comparisons to null or undefined if only one of them is possible?
Example:
get<string|undefined>() == null;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [use === undefined instead]
get<string|undefined|null>() == null; // still allowed| get<string | undefined>() == null; | ||
| get<string | null>() == undefined; | ||
| get<string | null>() == null; | ||
| get<string | undefined>() == undefined; |
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here the rule could suggest to use strict equality comparison
| get<string | undefined>() == null; | ||
| get<string | null>() == undefined; | ||
| get<string | null>() == null; | ||
| get<string | undefined>() == undefined; |
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Please add a test for the following:
get<null|undefined> == null;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [T]
get<null|undefined> != undefined;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [F]
nchen63
reviewed
Jan 16, 2017
| @@ -0,0 +1,210 @@ | |||
| /** | |||
| * @license | |||
| * Copyright 2016 Palantir Technologies, Inc. | |||
| @@ -178,6 +178,11 @@ export function isTypeFlagSet(type: ts.Type, flagToCheck: ts.TypeFlags): boolean | |||
| /* tslint:enable:no-bitwise */ | |||
| } | |||
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| /** Type predicate to test for a union type. */ | |||
| export function isUnionType(type: ts.Type): type is ts.UnionType { | |||
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utils shouldn't be cluttered with wrappers for isTypeFlagSet
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Would this rule make |
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@andy-hanson if it catches typos like |
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sorry, can you merge with master? |
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PR checklist
What changes did you make?
Added the
strict-type-predicatesrule, which warns fortypeof x === "string"wherexis always (or never) a string, and forx === undefinedwherexis always (or never)undefined.Is there anything you'd like reviewers to focus on?
Can't do
instanceofchecks yet as the type checker does not expose assignability checks. If it did, thegetTypePredicateForKindfunction could be removed.