Cache mapper instantiations (#61505)

Author: Andarist

src/compiler/checker.ts

@@ -2322,6 +2322,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     var inferenceContexts: (InferenceContext | undefined)[] = [];
     var inferenceContextCount = 0;
 
+    var activeTypeMappers: TypeMapper[] = [];
+    var activeTypeMappersCaches: Map<string, Type>[] = [];
+    var activeTypeMappersCount = 0;
+
     var emptyStringType = getStringLiteralType("");
     var zeroType = getNumberLiteralType(0);
     var zeroBigIntType = getBigIntLiteralType({ negative: false, base10Value: "0" });
@@ -20858,10 +20862,26 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             error(currentNode, Diagnostics.Type_instantiation_is_excessively_deep_and_possibly_infinite);
             return errorType;
         }
+        const index = findActiveMapper(mapper);
+        if (index === -1) {
+            pushActiveMapper(mapper);
+        }
+        const key = type.id + getAliasId(aliasSymbol, aliasTypeArguments);
+        const mapperCache = activeTypeMappersCaches[index !== -1 ? index : activeTypeMappersCount - 1];
+        const cached = mapperCache.get(key);
+        if (cached) {
+            return cached;
+        }
         totalInstantiationCount++;
         instantiationCount++;
         instantiationDepth++;
         const result = instantiateTypeWorker(type, mapper, aliasSymbol, aliasTypeArguments);
+        if (index === -1) {
+            popActiveMapper();
+        }
+        else {
+            mapperCache.set(key, result);
+        }
         instantiationDepth--;
         return result;
     }
@@ -27452,6 +27472,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     inference.inferredType = fallbackType && context.compareTypes(fallbackType, getTypeWithThisArgument(instantiatedConstraint, fallbackType)) ? fallbackType : instantiatedConstraint;
                 }
             }
+            clearActiveMapperCaches();
         }
 
         return inference.inferredType;
@@ -32668,6 +32689,31 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         }
     }
 
+    function pushActiveMapper(mapper: TypeMapper) {
+        activeTypeMappers[activeTypeMappersCount] = mapper;
+        activeTypeMappersCaches[activeTypeMappersCount] = new Map();
+        activeTypeMappersCount++;
+    }
+
+    function popActiveMapper() {
+        activeTypeMappersCount--;
+    }
+
+    function findActiveMapper(mapper: TypeMapper) {
+        for (let i = activeTypeMappersCount - 1; i >= 0; i--) {
+            if (mapper === activeTypeMappers[i]) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    function clearActiveMapperCaches() {
+        for (let i = activeTypeMappersCount - 1; i >= 0; i--) {
+            activeTypeMappersCaches[i].clear();
+        }
+    }
+
     function getContextualImportAttributeType(node: ImportAttribute) {
         return getTypeOfPropertyOfContextualType(getGlobalImportAttributesType(/*reportErrors*/ false), getNameFromImportAttribute(node));
     }

tests/baselines/reference/callsOnComplexSignatures.types

@@ -3,7 +3,7 @@
 === Performance Stats ===
 Assignability cache: 2,500
 Type Count: 10,000
-Instantiation count: 100,000
+Instantiation count: 50,000
 Symbol count: 50,000
 
 === callsOnComplexSignatures.tsx ===

tests/baselines/reference/checkJsxChildrenCanBeTupleType.types

@@ -3,7 +3,7 @@
 === Performance Stats ===
 Assignability cache: 2,500
 Type Count: 10,000
-Instantiation count: 100,000
+Instantiation count: 50,000
 Symbol count: 50,000
 
 === checkJsxChildrenCanBeTupleType.tsx ===

tests/baselines/reference/checkJsxChildrenProperty16.types

@@ -3,7 +3,7 @@
 === Performance Stats ===
 Assignability cache: 2,500
 Type Count: 10,000
-Instantiation count: 100,000
+Instantiation count: 50,000
 Symbol count: 50,000
 
 === checkJsxChildrenProperty16.tsx ===

tests/baselines/reference/checkJsxUnionSFXContextualTypeInferredCorrectly.types

@@ -3,7 +3,7 @@
 === Performance Stats ===
 Assignability cache: 2,500
 Type Count: 10,000
-Instantiation count: 100,000
+Instantiation count: 50,000
 Symbol count: 50,000
 
 === checkJsxUnionSFXContextualTypeInferredCorrectly.tsx ===

tests/baselines/reference/circularBaseConstraint.types

@@ -1,8 +1,5 @@
 //// [tests/cases/compiler/circularBaseConstraint.ts] ////
 
-=== Performance Stats ===
-Instantiation count: 2,500
-
 === circularBaseConstraint.ts ===
 // Repro from #54610
 

tests/baselines/reference/circularlySimplifyingConditionalTypesNoCrash.types

@@ -1,8 +1,5 @@
 //// [tests/cases/compiler/circularlySimplifyingConditionalTypesNoCrash.ts] ////
 
-=== Performance Stats ===
-Instantiation count: 2,500
-
 === circularlySimplifyingConditionalTypesNoCrash.ts ===
 type Omit<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>;
 >Omit : Omit<T, K>

tests/baselines/reference/conditionalTypeDiscriminatingLargeUnionRegularTypeFetchingSpeedReasonable.types

@@ -4,7 +4,7 @@
 Strict subtype cache: 2,500
 Assignability cache: 10,000
 Type Count: 10,000
-Instantiation count: 100,000
+Instantiation count: 50,000
 
 === conditionalTypeDiscriminatingLargeUnionRegularTypeFetchingSpeedReasonable.ts ===
 type BigUnion =

tests/baselines/reference/conditionalTypeDoesntSpinForever.types

@@ -2,7 +2,7 @@
 
 === Performance Stats ===
 Type Count: 1,000
-Instantiation count: 2,500 -> 5,000
+Instantiation count: 2,500
 
 === conditionalTypeDoesntSpinForever.ts ===
 // A *self-contained* demonstration of the problem follows...

tests/baselines/reference/conditionalTypeVarianceBigArrayConstraintsPerformance.types

@@ -3,7 +3,7 @@
 === Performance Stats ===
 Assignability cache: 1,000
 Type Count: 5,000
-Instantiation count: 100,000
+Instantiation count: 50,000
 Symbol count: 50,000
 
 === conditionalTypeVarianceBigArrayConstraintsPerformance.ts ===