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This cherry-pick was triggerd by a request on #34706
Please review the diff and merge if no changes are unexpected.
You can view the cherry-pick log here.

cc @sandersn

Component commits:
056a656 Restore delayed merge check to getTypeFromJSDocValueReference
This is needed when a function merges with a prototype assignment. The
resulting *merged* symbol is a constructor function marked with
SymbolFlags.Class. However, the merge doesn't happen until
getTypeOfFuncClassEnumModule is called, which, in the
getTypeReferenceType code path, doesn't happen until
getTypeFromJSDocValueReference. That means the check for
SymbolFlags.Class is missed.

Previously, getTypeFromJSDocValueReference had a weird check
`symbol !== getTypeOfSymbol(symbol).symbol`, which, if true, ran
getTypeReferenceType again on `getTypeOfSymbol(symbol).symbol`. For
JS "aliases", this had the effect of dereferencing the alias, and for
function-prototype merges, this had the effect of ... just trying again
after the merge had happened.

This is a confusing way to run things. getTypeReferenceType should
instead detect a function-prototype merge, cause it to happen, and
*then* run the rest of its code instead of relying on try-again logic at
the very end. However, for the RC, I want to fix this code by restoring
the old check, with an additional check to make sure that microsoft#33106 doesn't
break again:

```ts
const valueType = getTypeOfSymbol(symbol)
symbol !== valueType.symbol && getMergedSymbol(symbol) === valueType.symbol
```

I'll work on the real fix afterwards and put it into 3.8.

d1515f4 Add bug number
@sandersn sandersn merged commit 23d1b7b into microsoft:release-3.7 Oct 24, 2019
@microsoft microsoft locked as resolved and limited conversation to collaborators Oct 21, 2025
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2 participants