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instantiate conditional types without a combined mapper for the cache lookup #64601

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Max Schwenk (maschwenk) wants to merge 1 commit into from
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instantiate conditional types without a combined mapper for the cache lookup #64601

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18 changes: 16 additions & 2 deletions tsc/internal/checker/checker.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22721,7 +22721,7 @@ func (c *Checker) instantiateTypeWorker(t *Type, m *TypeMapper, alias *TypeAlias
case flags&TypeFlagsStringMapping != 0:
return c.getStringMappingType(t.symbol, c.instantiateType(t.AsStringMappingType().target, m))
case flags&TypeFlagsConditional != 0:
return c.getConditionalTypeInstantiation(t, c.combineTypeMappers(t.AsConditionalType().mapper, m), false /*forConstraint*/, alias)
return c.getConditionalTypeInstantiationEx(t, t.AsConditionalType().mapper, m, false /*forConstraint*/, alias)
case flags&TypeFlagsSubstitution != 0:
newBaseType := c.instantiateType(t.AsSubstitutionType().baseType, m)
if c.isNoInferType(t) {
Expand Down Expand Up @@ -22932,12 +22932,26 @@ func (c *Checker) instantiateAnonymousType(t *Type, m *TypeMapper, alias *TypeAl
}

func (c *Checker) getConditionalTypeInstantiation(t *Type, mapper *TypeMapper, forConstraint bool, alias *TypeAlias) *Type {
return c.getConditionalTypeInstantiationEx(t, nil, mapper, forConstraint, alias)
}

// Instantiates t with combineTypeMappers(m1, mapper) without creating the combined mapper, which
// is only needed for the type arguments.
func (c *Checker) getConditionalTypeInstantiationEx(t *Type, m1 *TypeMapper, mapper *TypeMapper, forConstraint bool, alias *TypeAlias) *Type {
root := t.AsConditionalType().root
if len(root.outerTypeParameters) != 0 {
// We are instantiating a conditional type that has one or more type parameters in scope. Apply the
// mapper to the type parameters to produce the effective list of type arguments, and compute the
// instantiation cache key from the type IDs of the type arguments.
typeArguments := core.Map(root.outerTypeParameters, mapper.Map)
typeArguments := core.Map(root.outerTypeParameters, func(t *Type) *Type {
// What CompositeTypeMapper.Map does.
if m1 != nil {
if t1 := m1.Map(t); t1 != t {
return c.instantiateType(t1, mapper)
}
}
return mapper.Map(t)
})
key := getConditionalTypeKey(typeArguments, alias, forConstraint)
result := root.instantiations[key]
if result == nil {
Expand Down