Add flag to change catch variables' default types to unknown

src/compiler/checker.ts

@@ -354,6 +354,7 @@ namespace ts {
         const strictPropertyInitialization = getStrictOptionValue(compilerOptions, "strictPropertyInitialization");
         const noImplicitAny = getStrictOptionValue(compilerOptions, "noImplicitAny");
         const noImplicitThis = getStrictOptionValue(compilerOptions, "noImplicitThis");
+        const useUnknownInCatchVariables = getStrictOptionValue(compilerOptions, "useUnknownInCatchVariables");
         const keyofStringsOnly = !!compilerOptions.keyofStringsOnly;
         const freshObjectLiteralFlag = compilerOptions.suppressExcessPropertyErrors ? 0 : ObjectFlags.FreshLiteral;
 
@@ -8929,7 +8930,7 @@ namespace ts {
             if (isCatchClauseVariableDeclarationOrBindingElement(declaration)) {
                 const typeNode = getEffectiveTypeAnnotationNode(declaration);
                 if (typeNode === undefined) {
-                    return anyType;
+                    return useUnknownInCatchVariables ? unknownType : anyType;
                 }
                 const type = getTypeOfNode(typeNode);
                 // an errorType will make `checkTryStatement` issue an error

src/compiler/commandLineParser.ts

@@ -688,6 +688,14 @@ namespace ts {
             category: Diagnostics.Additional_Checks,
             description: Diagnostics.Require_undeclared_properties_from_index_signatures_to_use_element_accesses
         },
+        {
+            name: "useUnknownInCatchVariables",
+            type: "boolean",
+            affectsSemanticDiagnostics: true,
+            showInSimplifiedHelpView: true,
+            category: Diagnostics.Additional_Checks,
+            description: Diagnostics.Type_catch_clause_variables_as_unknown_instead_of_any,
+        },
 
         // Module Resolution
         {

src/compiler/diagnosticMessages.json

@@ -5095,6 +5095,10 @@
         "category": "Message",
         "code": 6802
     },
+    "Type catch clause variables as 'unknown' instead of 'any'.": {
+        "category": "Message",
+        "code": 6803
+    },
 
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",

src/compiler/types.ts

@@ -6006,6 +6006,7 @@ namespace ts {
         /* @internal */ suppressOutputPathCheck?: boolean;
         target?: ScriptTarget; // TODO: GH#18217 frequently asserted as defined
         traceResolution?: boolean;
+        useUnknownInCatchVariables?: boolean;
         resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to compute primary types search locations */

src/compiler/utilities.ts

@@ -6067,6 +6067,7 @@ namespace ts {
         | "strictBindCallApply"
         | "strictPropertyInitialization"
         | "alwaysStrict"
+        | "useUnknownInCatchVariables"
         ;
 
     export function getStrictOptionValue(compilerOptions: CompilerOptions, flag: StrictOptionName): boolean {

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2896,6 +2896,7 @@ declare namespace ts {
         suppressImplicitAnyIndexErrors?: boolean;
         target?: ScriptTarget;
         traceResolution?: boolean;
+        useUnknownInCatchVariables?: boolean;
         resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to compute primary types search locations */

tests/baselines/reference/api/typescript.d.ts

@@ -2896,6 +2896,7 @@ declare namespace ts {
         suppressImplicitAnyIndexErrors?: boolean;
         target?: ScriptTarget;
         traceResolution?: boolean;
+        useUnknownInCatchVariables?: boolean;
         resolveJsonModule?: boolean;
         types?: string[];
         /** Paths used to compute primary types search locations */

tests/baselines/reference/controlFlowForCatchAndFinally.types

@@ -120,7 +120,7 @@ class Foo {
 >Aborter : typeof Aborter
 
         } catch (error) {
->error : any
+>error : unknown
 
             if (this.abortController !== undefined) {
 >this.abortController !== undefined : boolean

tests/baselines/reference/showConfig/Shows tsconfig for single option/useUnknownInCatchVariables/tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "useUnknownInCatchVariables": true
+    }
+}

tests/baselines/reference/tryCatchFinallyControlFlow.types

@@ -19,10 +19,10 @@ function f1() {
 >a : number
     }
     catch (e) {
->e : any
+>e : unknown
 
         throw e;
->e : any
+>e : unknown
     }
     finally {
         if (a != null && a.toFixed(0) == "123") { 
@@ -55,15 +55,15 @@ function f2() {
 >1 : 1
     }
     catch (e) {
->e : any
+>e : unknown
 
         x = 2;
 >x = 2 : 2
 >x : 0 | 1 | 2 | 3
 >2 : 2
 
         throw e;
->e : any
+>e : unknown
     }
     finally {
         x;  // 0 | 1 | 2
@@ -87,7 +87,7 @@ function f3() {
 >1 : 1
     }
     catch (e) {
->e : any
+>e : unknown
 
         x = 2;
 >x = 2 : 2
@@ -118,7 +118,7 @@ function f4() {
 >1 : 1
     }
     catch (e) {
->e : any
+>e : unknown
 
         x = 2;
 >x = 2 : 2
@@ -149,7 +149,7 @@ function f5() {
         return;
     }
     catch (e) {
->e : any
+>e : unknown
 
         x = 2;
 >x = 2 : 2
@@ -178,7 +178,7 @@ function f6() {
 >1 : 1
     }
     catch (e) {
->e : any
+>e : unknown
 
         x = 2;
 >x = 2 : 2
@@ -211,7 +211,7 @@ function f7() {
         return;
     }
     catch (e) {
->e : any
+>e : unknown
 
         x = 2;
 >x = 2 : 2
@@ -324,7 +324,7 @@ function f10() {
             return;
         }
         catch (e) {
->e : any
+>e : unknown
 
             x = 2;
 >x = 2 : 2
@@ -388,7 +388,7 @@ function f11() {
             }
         }
         catch (e) {
->e : any
+>e : unknown
 
             x;  // 0 | 1 | 2
 >x : 0 | 1 | 2
@@ -466,7 +466,7 @@ function f12() {
             }
         }
         catch (e) {
->e : any
+>e : unknown
 
             x;  // 0 | 1 | 2
 >x : 0 | 1 | 2
@@ -576,7 +576,7 @@ function t1() {
 >'x' : "x"
         }
         catch (e) {
->e : any
+>e : unknown
 
             return null;
 >null : null
@@ -626,7 +626,7 @@ function notallowed(arg: number) {
         finally { }
     }
     catch (err) {
->err : any
+>err : unknown
 
         state.tag;
 >state.tag : "one" | "two" | "three"
@@ -770,7 +770,7 @@ function f21() {
 >x : 3 | 4 | 5
     }
     catch (e) {
->e : any
+>e : unknown
 
         x;  // 0 | 1 | 2 | 3 | 4 | 5
 >x : 0 | 1 | 2 | 3 | 4 | 5

tests/baselines/reference/tsConfig/Default initialized TSConfig/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with advanced options/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with boolean value compiler options/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with enum value compiler options/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with files options/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with incorrect compiler option value/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with incorrect compiler option/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with list compiler options with enum value/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsConfig/Initialized TSConfig with list compiler options/tsconfig.json

@@ -42,6 +42,7 @@
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tsc/runWithoutArgs/initial-build/show-help-with-ExitStatus.DiagnosticsPresent_OutputsSkipped.js

@@ -48,6 +48,7 @@ Options:
  --noUnusedParameters                               Report errors on unused parameters.
  --noImplicitReturns                                Report error when not all code paths in function return a value.
  --noFallthroughCasesInSwitch                       Report errors for fallthrough cases in switch statement.
+ --useUnknownInCatchVariables                       Type catch clause variables as 'unknown' instead of 'any'.
  --types                                            Type declaration files to be included in compilation.
  --esModuleInterop                                  Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'.
  @<file>                                            Insert command line options and files from a file.

tests/baselines/reference/tscWatch/programUpdates/should-not-trigger-recompilation-because-of-program-emit/declarationDir-is-specified.js

@@ -63,6 +63,7 @@ interface Array<T> { length: number; [n: number]: T; }
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tscWatch/programUpdates/should-not-trigger-recompilation-because-of-program-emit/when-outDir-and-declarationDir-is-specified.js

@@ -63,6 +63,7 @@ interface Array<T> { length: number; [n: number]: T; }
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tscWatch/programUpdates/should-not-trigger-recompilation-because-of-program-emit/when-outDir-is-specified.js

@@ -63,6 +63,7 @@ interface Array<T> { length: number; [n: number]: T; }
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tscWatch/programUpdates/should-not-trigger-recompilation-because-of-program-emit/with-outFile.js

@@ -63,6 +63,7 @@ interface Array<T> { length: number; [n: number]: T; }
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tscWatch/programUpdates/should-not-trigger-recompilation-because-of-program-emit/without-outDir-or-outFile-is-specified-with-declaration-enabled.js

@@ -63,6 +63,7 @@ interface Array<T> { length: number; [n: number]: T; }
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/tscWatch/programUpdates/should-not-trigger-recompilation-because-of-program-emit/without-outDir-or-outFile-is-specified.js

@@ -63,6 +63,7 @@ interface Array<T> { length: number; [n: number]: T; }
     // "noUncheckedIndexedAccess": true,            /* Include 'undefined' in index signature results */
     // "noImplicitOverride": true,                  /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
     // "noPropertyAccessFromIndexSignature": true,  /* Require undeclared properties from index signatures to use element accesses. */
+    // "useUnknownInCatchVariables": true,          /* Type catch clause variables as 'unknown' instead of 'any'. */
 
     /* Module Resolution Options */
     // "moduleResolution": "node",                  /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

tests/baselines/reference/typedefOnStatements.types

@@ -68,7 +68,7 @@ throw new Error('Unreachable')
 try {
 }
 catch (e) {
->e : any
+>e : unknown
 }
 
 /**