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Fix target library hints for readonly interfaces and tuples #64970

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c72c5e4
Fix target library suggestions for readonly interfaces
maheshrijal Oct 26, 2026
24ed7b0
Keep readonly library tests focused on diagnostics
maheshrijal Oct 26, 2026
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7 changes: 6 additions & 1 deletion tsc/internal/checker/checker.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11830,7 +11830,12 @@ func (c *Checker) reportNonexistentProperty(propNode *ast.Node, containingType *
}

func (c *Checker) getSuggestedLibForNonExistentProperty(missingProperty string, containingType *Type) string {
container := c.getApparentType(containingType).symbol
t := c.getApparentType(containingType)
if isTupleType(t) {
// Tuple types have no symbol; use their Array or ReadonlyArray base.
t = core.IfElse(t.TargetTupleType().readonly, c.globalReadonlyArrayType, c.globalArrayType)
}
container := t.symbol
if container != nil {
featureMap := getFeatureMap()
if typeFeatures, ok := featureMap[container.Name()]; ok {
Expand Down
23 changes: 23 additions & 0 deletions tsc/internal/checker/utilities.go
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Expand Up @@ -1421,6 +1421,14 @@ var getFeatureMap = sync.OnceValue(func() map[string][]FeatureMapEntry {
{lib: "es2022", props: []string{"at"}},
{lib: "es2023", props: []string{"findLastIndex", "findLast", "toReversed", "toSorted", "toSpliced", "with"}},
},
"ReadonlyArray": {
{lib: "es5", props: []string{}},
{lib: "es2015", props: []string{"find", "findIndex", "entries", "keys", "values"}},
{lib: "es2016", props: []string{"includes"}},
{lib: "es2019", props: []string{"flat", "flatMap"}},
{lib: "es2022", props: []string{"at"}},
{lib: "es2023", props: []string{"findLastIndex", "findLast", "toReversed", "toSorted", "toSpliced", "with"}},
},
"Iterator": {
{lib: "es2015", props: []string{}},
},
Expand Down Expand Up @@ -1525,6 +1533,9 @@ var getFeatureMap = sync.OnceValue(func() map[string][]FeatureMapEntry {
"getOrInsertComputed",
}},
},
"ReadonlyMap": {
{lib: "es2015", props: []string{"entries", "keys", "values"}},
},
"MapConstructor": {
{lib: "es2024", props: []string{"groupBy"}},
},
Expand All @@ -1540,6 +1551,18 @@ var getFeatureMap = sync.OnceValue(func() map[string][]FeatureMapEntry {
"isDisjointFrom",
}},
},
"ReadonlySet": {
{lib: "es2015", props: []string{"entries", "keys", "values"}},
{lib: "es2025", props: []string{
"union",
"intersection",
"difference",
"symmetricDifference",
"isSubsetOf",
"isSupersetOf",
"isDisjointFrom",
}},
},
"PromiseConstructor": {
{lib: "es2015", props: []string{"all", "race", "reject", "resolve"}},
{lib: "es2020", props: []string{"allSettled"}},
Expand Down
132 changes: 132 additions & 0 deletions ...s/reference/compiler/doYouNeedToChangeYourTargetLibraryReadonly(target=es2015).errors.txt
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@@ -0,0 +1,132 @@
doYouNeedToChangeYourTargetLibraryReadonly.ts(7,7): error TS2550: Property 'includes' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2016' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(8,7): error TS2550: Property 'flat' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2019' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(9,7): error TS2550: Property 'flatMap' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2019' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(10,7): error TS2550: Property 'at' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2022' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(11,7): error TS2550: Property 'findLastIndex' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(12,7): error TS2550: Property 'findLast' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(13,7): error TS2550: Property 'toReversed' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(14,7): error TS2550: Property 'toSorted' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(15,7): error TS2550: Property 'toSpliced' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(16,7): error TS2550: Property 'with' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(19,15): error TS2550: Property 'toReversed' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(20,22): error TS2550: Property 'toReversed' does not exist on type 'readonly [1, 2, 3]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(23,7): error TS2550: Property 'toReversed' does not exist on type '[number, string]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(26,11): error TS2550: Property 'toReversed' does not exist on type 'T'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(38,5): error TS2550: Property 'union' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(39,5): error TS2550: Property 'intersection' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(40,5): error TS2550: Property 'difference' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(41,5): error TS2550: Property 'symmetricDifference' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(42,5): error TS2550: Property 'isSubsetOf' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(43,5): error TS2550: Property 'isSupersetOf' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(44,5): error TS2550: Property 'isDisjointFrom' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
doYouNeedToChangeYourTargetLibraryReadonly.ts(46,7): error TS2339: Property 'fill' does not exist on type 'readonly number[]'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(47,7): error TS2339: Property 'copyWithin' does not exist on type 'readonly number[]'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(48,7): error TS2339: Property 'notAnArrayMethod' does not exist on type 'readonly number[]'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(49,5): error TS2339: Property 'getOrInsert' does not exist on type 'ReadonlyMap<string, number>'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(50,5): error TS2339: Property 'getOrInsertComputed' does not exist on type 'ReadonlyMap<string, number>'.


==== doYouNeedToChangeYourTargetLibraryReadonly.ts (26 errors) ====
declare const array: ReadonlyArray<number>;
array.find;
array.findIndex;
array.entries;
array.keys;
array.values;
array.includes;
~~~~~~~~
!!! error TS2550: Property 'includes' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2016' or later.
array.flat;
~~~~
!!! error TS2550: Property 'flat' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2019' or later.
array.flatMap;
~~~~~~~
!!! error TS2550: Property 'flatMap' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2019' or later.
array.at;
~~
!!! error TS2550: Property 'at' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2022' or later.
array.findLastIndex;
~~~~~~~~~~~~~
!!! error TS2550: Property 'findLastIndex' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
array.findLast;
~~~~~~~~
!!! error TS2550: Property 'findLast' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
array.toReversed;
~~~~~~~~~~
!!! error TS2550: Property 'toReversed' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
array.toSorted;
~~~~~~~~
!!! error TS2550: Property 'toSorted' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
array.toSpliced;
~~~~~~~~~
!!! error TS2550: Property 'toSpliced' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
array.with;
~~~~
!!! error TS2550: Property 'with' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.

declare const readonlyArray: readonly number[];
readonlyArray.toReversed;
~~~~~~~~~~
!!! error TS2550: Property 'toReversed' does not exist on type 'readonly number[]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
([1, 2, 3] as const).toReversed();
~~~~~~~~~~
!!! error TS2550: Property 'toReversed' does not exist on type 'readonly [1, 2, 3]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.

declare const tuple: [number, string];
tuple.toReversed;
~~~~~~~~~~
!!! error TS2550: Property 'toReversed' does not exist on type '[number, string]'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.

function f<T extends readonly number[]>(value: T) {
value.toReversed;
~~~~~~~~~~
!!! error TS2550: Property 'toReversed' does not exist on type 'T'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2023' or later.
}

declare const map: ReadonlyMap<string, number>;
map.entries;
map.keys;
map.values;

declare const set: ReadonlySet<number>;
set.entries;
set.keys;
set.values;
set.union;
~~~~~
!!! error TS2550: Property 'union' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
set.intersection;
~~~~~~~~~~~~
!!! error TS2550: Property 'intersection' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
set.difference;
~~~~~~~~~~
!!! error TS2550: Property 'difference' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
set.symmetricDifference;
~~~~~~~~~~~~~~~~~~~
!!! error TS2550: Property 'symmetricDifference' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
set.isSubsetOf;
~~~~~~~~~~
!!! error TS2550: Property 'isSubsetOf' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
set.isSupersetOf;
~~~~~~~~~~~~
!!! error TS2550: Property 'isSupersetOf' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.
set.isDisjointFrom;
~~~~~~~~~~~~~~
!!! error TS2550: Property 'isDisjointFrom' does not exist on type 'ReadonlySet<number>'. Do you need to change your target library? Try changing the 'lib' compiler option to 'es2025' or later.

array.fill;
~~~~
!!! error TS2339: Property 'fill' does not exist on type 'readonly number[]'.
array.copyWithin;
~~~~~~~~~~
!!! error TS2339: Property 'copyWithin' does not exist on type 'readonly number[]'.
array.notAnArrayMethod;
~~~~~~~~~~~~~~~~
!!! error TS2339: Property 'notAnArrayMethod' does not exist on type 'readonly number[]'.
map.getOrInsert;
~~~~~~~~~~~
!!! error TS2339: Property 'getOrInsert' does not exist on type 'ReadonlyMap<string, number>'.
map.getOrInsertComputed;
~~~~~~~~~~~~~~~~~~~
!!! error TS2339: Property 'getOrInsertComputed' does not exist on type 'ReadonlyMap<string, number>'.

69 changes: 69 additions & 0 deletions ...s/reference/compiler/doYouNeedToChangeYourTargetLibraryReadonly(target=esnext).errors.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,69 @@
doYouNeedToChangeYourTargetLibraryReadonly.ts(46,7): error TS2339: Property 'fill' does not exist on type 'readonly number[]'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(47,7): error TS2339: Property 'copyWithin' does not exist on type 'readonly number[]'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(48,7): error TS2339: Property 'notAnArrayMethod' does not exist on type 'readonly number[]'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(49,5): error TS2339: Property 'getOrInsert' does not exist on type 'ReadonlyMap<string, number>'.
doYouNeedToChangeYourTargetLibraryReadonly.ts(50,5): error TS2339: Property 'getOrInsertComputed' does not exist on type 'ReadonlyMap<string, number>'.


==== doYouNeedToChangeYourTargetLibraryReadonly.ts (5 errors) ====
declare const array: ReadonlyArray<number>;
array.find;
array.findIndex;
array.entries;
array.keys;
array.values;
array.includes;
array.flat;
array.flatMap;
array.at;
array.findLastIndex;
array.findLast;
array.toReversed;
array.toSorted;
array.toSpliced;
array.with;

declare const readonlyArray: readonly number[];
readonlyArray.toReversed;
([1, 2, 3] as const).toReversed();

declare const tuple: [number, string];
tuple.toReversed;

function f<T extends readonly number[]>(value: T) {
value.toReversed;
}

declare const map: ReadonlyMap<string, number>;
map.entries;
map.keys;
map.values;

declare const set: ReadonlySet<number>;
set.entries;
set.keys;
set.values;
set.union;
set.intersection;
set.difference;
set.symmetricDifference;
set.isSubsetOf;
set.isSupersetOf;
set.isDisjointFrom;

array.fill;
~~~~
!!! error TS2339: Property 'fill' does not exist on type 'readonly number[]'.
array.copyWithin;
~~~~~~~~~~
!!! error TS2339: Property 'copyWithin' does not exist on type 'readonly number[]'.
array.notAnArrayMethod;
~~~~~~~~~~~~~~~~
!!! error TS2339: Property 'notAnArrayMethod' does not exist on type 'readonly number[]'.
map.getOrInsert;
~~~~~~~~~~~
!!! error TS2339: Property 'getOrInsert' does not exist on type 'ReadonlyMap<string, number>'.
map.getOrInsertComputed;
~~~~~~~~~~~~~~~~~~~
!!! error TS2339: Property 'getOrInsertComputed' does not exist on type 'ReadonlyMap<string, number>'.

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