Port PR #61376: Fix spurious "used before being assigned" errors in for of/in loops

internal/checker/checker.go

@@ -10806,9 +10806,9 @@ func (c *Checker) checkIdentifier(node *ast.Node, checkMode CheckMode) *Type {
 	// We only look for uninitialized variables in strict null checking mode, and only when we can analyze
 	// the entire control flow graph from the variable's declaration (i.e. when the flow container and
 	// declaration container are the same).
-	isNeverInitialized := immediateDeclaration != nil && ast.IsVariableDeclaration(immediateDeclaration) && immediateDeclaration.Initializer() == nil &&
-		immediateDeclaration.AsVariableDeclaration().ExclamationToken == nil && c.isMutableLocalVariableDeclaration(immediateDeclaration) &&
-		!c.isSymbolAssignedDefinitely(symbol)
+	isNeverInitialized := immediateDeclaration != nil && ast.IsVariableDeclaration(immediateDeclaration) && !ast.IsForInOrOfStatement(immediateDeclaration.Parent.Parent) &&
+		immediateDeclaration.Initializer() == nil && immediateDeclaration.AsVariableDeclaration().ExclamationToken == nil &&
+		c.isMutableLocalVariableDeclaration(immediateDeclaration) && !c.isSymbolAssignedDefinitely(symbol)
 	assumeInitialized := isParameter ||
 		isAlias ||
 		(isOuterVariable && !isNeverInitialized) ||

testdata/baselines/reference/compiler/unusedLocalsInForInOrOf1.errors.txt

@@ -0,0 +1,84 @@
+unusedLocalsInForInOrOf1.ts(2,12): error TS6133: 'f' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(8,7): error TS6133: 'f' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(14,12): error TS6133: 'g' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(20,12): error TS6133: 'f2' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(26,7): error TS6133: 'f2' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(32,12): error TS6133: 'g2' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(38,12): error TS6133: 'f3' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(44,7): error TS6133: 'f3' is declared but its value is never read.
+unusedLocalsInForInOrOf1.ts(50,12): error TS6133: 'g3' is declared but its value is never read.
+
+
+==== unusedLocalsInForInOrOf1.ts (9 errors) ====
+    for (let x of [1, 2]) {
+      function f() {
+               ~
+!!! error TS6133: 'f' is declared but its value is never read.
+        x;
+      }
+    }
+
+    for (let x of [1, 2]) {
+      let f = () => {
+          ~
+!!! error TS6133: 'f' is declared but its value is never read.
+        x;
+      };
+    }
+
+    for (const x of [1, 2]) {
+      function g() {
+               ~
+!!! error TS6133: 'g' is declared but its value is never read.
+        x;
+      }
+    }
+
+    for (let x in { a: 1, b: 2 }) {
+      function f2() {
+               ~~
+!!! error TS6133: 'f2' is declared but its value is never read.
+        x;
+      }
+    }
+
+    for (let x in { a: 1, b: 2 }) {
+      let f2 = () => {
+          ~~
+!!! error TS6133: 'f2' is declared but its value is never read.
+        x;
+      };
+    }
+
+    for (const x in { a: 1, b: 2 }) {
+      function g2() {
+               ~~
+!!! error TS6133: 'g2' is declared but its value is never read.
+        x;
+      }
+    }
+
+    for (let { x } of [{ x: 1 }, { x: 2 }]) {
+      function f3() {
+               ~~
+!!! error TS6133: 'f3' is declared but its value is never read.
+        x;
+      }
+    }
+
+    for (let { x } of [{ x: 1 }, { x: 2 }]) {
+      let f3 = () => {
+          ~~
+!!! error TS6133: 'f3' is declared but its value is never read.
+        x;
+      };
+    }
+
+    for (const { x } of [{ x: 1 }, { x: 2 }]) {
+      function g3() {
+               ~~
+!!! error TS6133: 'g3' is declared but its value is never read.
+        x;
+      }
+    }
+

testdata/baselines/reference/compiler/unusedLocalsInForInOrOf1.symbols

@@ -0,0 +1,117 @@
+//// [tests/cases/compiler/unusedLocalsInForInOrOf1.ts] ////
+
+=== unusedLocalsInForInOrOf1.ts ===
+for (let x of [1, 2]) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 0, 8))
+
+  function f() {
+>f : Symbol(f, Decl(unusedLocalsInForInOrOf1.ts, 0, 23))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 0, 8))
+  }
+}
+
+for (let x of [1, 2]) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 6, 8))
+
+  let f = () => {
+>f : Symbol(f, Decl(unusedLocalsInForInOrOf1.ts, 7, 5))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 6, 8))
+
+  };
+}
+
+for (const x of [1, 2]) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 12, 10))
+
+  function g() {
+>g : Symbol(g, Decl(unusedLocalsInForInOrOf1.ts, 12, 25))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 12, 10))
+  }
+}
+
+for (let x in { a: 1, b: 2 }) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 18, 8))
+>a : Symbol(a, Decl(unusedLocalsInForInOrOf1.ts, 18, 15))
+>b : Symbol(b, Decl(unusedLocalsInForInOrOf1.ts, 18, 21))
+
+  function f2() {
+>f2 : Symbol(f2, Decl(unusedLocalsInForInOrOf1.ts, 18, 31))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 18, 8))
+  }
+}
+
+for (let x in { a: 1, b: 2 }) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 24, 8))
+>a : Symbol(a, Decl(unusedLocalsInForInOrOf1.ts, 24, 15))
+>b : Symbol(b, Decl(unusedLocalsInForInOrOf1.ts, 24, 21))
+
+  let f2 = () => {
+>f2 : Symbol(f2, Decl(unusedLocalsInForInOrOf1.ts, 25, 5))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 24, 8))
+
+  };
+}
+
+for (const x in { a: 1, b: 2 }) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 30, 10))
+>a : Symbol(a, Decl(unusedLocalsInForInOrOf1.ts, 30, 17))
+>b : Symbol(b, Decl(unusedLocalsInForInOrOf1.ts, 30, 23))
+
+  function g2() {
+>g2 : Symbol(g2, Decl(unusedLocalsInForInOrOf1.ts, 30, 33))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 30, 10))
+  }
+}
+
+for (let { x } of [{ x: 1 }, { x: 2 }]) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 10))
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 20))
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 30))
+
+  function f3() {
+>f3 : Symbol(f3, Decl(unusedLocalsInForInOrOf1.ts, 36, 41))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 36, 10))
+  }
+}
+
+for (let { x } of [{ x: 1 }, { x: 2 }]) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 10))
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 20))
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 30))
+
+  let f3 = () => {
+>f3 : Symbol(f3, Decl(unusedLocalsInForInOrOf1.ts, 43, 5))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 42, 10))
+
+  };
+}
+
+for (const { x } of [{ x: 1 }, { x: 2 }]) {
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 12))
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 22))
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 32))
+
+  function g3() {
+>g3 : Symbol(g3, Decl(unusedLocalsInForInOrOf1.ts, 48, 43))
+
+    x;
+>x : Symbol(x, Decl(unusedLocalsInForInOrOf1.ts, 48, 12))
+  }
+}
+

testdata/baselines/reference/compiler/unusedLocalsInForInOrOf1.types

@@ -0,0 +1,153 @@
+//// [tests/cases/compiler/unusedLocalsInForInOrOf1.ts] ////
+
+=== unusedLocalsInForInOrOf1.ts ===
+for (let x of [1, 2]) {
+>x : number
+>[1, 2] : number[]
+>1 : 1
+>2 : 2
+
+  function f() {
+>f : () => void
+
+    x;
+>x : number
+  }
+}
+
+for (let x of [1, 2]) {
+>x : number
+>[1, 2] : number[]
+>1 : 1
+>2 : 2
+
+  let f = () => {
+>f : () => void
+>() => {    x;  } : () => void
+
+    x;
+>x : number
+
+  };
+}
+
+for (const x of [1, 2]) {
+>x : number
+>[1, 2] : number[]
+>1 : 1
+>2 : 2
+
+  function g() {
+>g : () => void
+
+    x;
+>x : number
+  }
+}
+
+for (let x in { a: 1, b: 2 }) {
+>x : string
+>{ a: 1, b: 2 } : { a: number; b: number; }
+>a : number
+>1 : 1
+>b : number
+>2 : 2
+
+  function f2() {
+>f2 : () => void
+
+    x;
+>x : string
+  }
+}
+
+for (let x in { a: 1, b: 2 }) {
+>x : string
+>{ a: 1, b: 2 } : { a: number; b: number; }
+>a : number
+>1 : 1
+>b : number
+>2 : 2
+
+  let f2 = () => {
+>f2 : () => void
+>() => {    x;  } : () => void
+
+    x;
+>x : string
+
+  };
+}
+
+for (const x in { a: 1, b: 2 }) {
+>x : string
+>{ a: 1, b: 2 } : { a: number; b: number; }
+>a : number
+>1 : 1
+>b : number
+>2 : 2
+
+  function g2() {
+>g2 : () => void
+
+    x;
+>x : string
+  }
+}
+
+for (let { x } of [{ x: 1 }, { x: 2 }]) {
+>x : number
+>[{ x: 1 }, { x: 2 }] : { x: number; }[]
+>{ x: 1 } : { x: number; }
+>x : number
+>1 : 1
+>{ x: 2 } : { x: number; }
+>x : number
+>2 : 2
+
+  function f3() {
+>f3 : () => void
+
+    x;
+>x : number
+  }
+}
+
+for (let { x } of [{ x: 1 }, { x: 2 }]) {
+>x : number
+>[{ x: 1 }, { x: 2 }] : { x: number; }[]
+>{ x: 1 } : { x: number; }
+>x : number
+>1 : 1
+>{ x: 2 } : { x: number; }
+>x : number
+>2 : 2
+
+  let f3 = () => {
+>f3 : () => void
+>() => {    x;  } : () => void
+
+    x;
+>x : number
+
+  };
+}
+
+for (const { x } of [{ x: 1 }, { x: 2 }]) {
+>x : number
+>[{ x: 1 }, { x: 2 }] : { x: number; }[]
+>{ x: 1 } : { x: number; }
+>x : number
+>1 : 1
+>{ x: 2 } : { x: number; }
+>x : number
+>2 : 2
+
+  function g3() {
+>g3 : () => void
+
+    x;
+>x : number
+  }
+}
+