fix(language-service): show narrowed type for @let declarations in hover#66836
fix(language-service): show narrowed type for @let declarations in hover#66836TejasSathe010 wants to merge 1 commit intoangular:mainfrom
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When hovering over a `@let` declaration variable inside a control flow block (e.g., `@if`), the Language Service now shows the flow-narrowed type instead of the original declaration type. The fix retrieves type information from the TCB at the usage location where TypeScript has applied flow narrowing, rather than from the declaration location. Fixes angular#65491
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area: language-service
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| import {LanguageServiceTestEnv, Project} from '../testing'; | ||
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| describe('let declarations narrowing', () => { |
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this should be in the quick info suite not its own file
| * Gets the TCB location for a template node at its usage site. | ||
| * This is useful for getting flow-narrowed types for variables. | ||
| */ | ||
| getTcbLocation(node: AST | TmplAstNode): TcbLocation | null { |
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the tcbLocation should probably be on the LetDeclarationSymbol when constructed rather than having to grab it later. e.g.
/**
* The location in the TCB where this symbol is used or declared.
* For a declaration, this matches `localVarLocation`.
* For a usage, this is the location of the node usage in the TCB.
*/
tcbLocation: TcbLocation;
I would guess this is also an issue with ReferenceSymbol and VariableSymbol for references (<div #IAmARef) and varaibles (*ngFor variables)?
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When hovering over a
@letdeclaration variable inside a control flow block (e.g.,@if), the Language Service now shows the flow-narrowed type instead of the original declaration type.The fix retrieves type information from the TCB at the usage location where TypeScript has applied flow narrowing, rather than from the declaration location.
Fixes #65491
PR Checklist
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PR Type
What kind of change does this PR introduce?
What is the current behavior?
When hovering over a @let variable inside a narrowed scope (e.g., @if (obj !== null)), the Language Service shows the original declaration type including null.
Issue Number: #65491
What is the new behavior?
The hover tooltip now shows the flow-narrowed type, matching what the Angular compiler uses for type checking.
Does this PR introduce a breaking change?
Other information
Issue reported on: Angular v19.2.5 with Language Service Extension v20.1.1
Validated on: Angular main branch (21.1.0-next.1)
Root cause: getQuickInfoForLetDeclarationSymbol() queried TypeScript at the declaration location in the TCB, not the usage location where flow narrowing applies.
Fix: Added getTcbLocationOfNode() to TemplateTypeChecker to find the TCB node at the usage site. Updated QuickInfoBuilder to use this method for @let declarations, with graceful fallback to the original behavior. This follows the same pattern used by getQuickInfoForBindingSymbol and getQuickInfoForPipeSymbol.