prefer-const: don't treat index signatures as parameters (palantir#3385)

The `k` in `{[k: string]: string}` is a `ts.ParameterDeclaration`. This should not be treated like a parameter in the value domain.
HyphnKnight · Apr 9, 2018 · 75be9a1 · 75be9a1
1 parent fc27808
commit 75be9a1
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Showing 3 changed files with 20 additions and 4 deletions.
diff --git a/src/rules/preferConstRule.ts b/src/rules/preferConstRule.ts
@@ -175,10 +175,12 @@ class PreferConstWalker extends Lint.AbstractWalker<Options> {
                     });
                 }
             } else if (node.kind === ts.SyntaxKind.Parameter) {
-                this.handleBindingName((node as ts.ParameterDeclaration).name, {
-                    canBeConst: false,
-                    isBlockScoped: true,
-                });
+                if (node.parent!.kind !== ts.SyntaxKind.IndexSignature) {
+                    this.handleBindingName((node as ts.ParameterDeclaration).name, {
+                        canBeConst: false,
+                        isBlockScoped: true,
+                    });
+                }
             } else if (utils.isPostfixUnaryExpression(node) ||
                        utils.isPrefixUnaryExpression(node) &&
                        (node.operator === ts.SyntaxKind.PlusPlusToken || node.operator === ts.SyntaxKind.MinusMinusToken)) {

diff --git a/test/rules/prefer-const/default/test.ts.fix b/test/rules/prefer-const/default/test.ts.fix
@@ -219,3 +219,10 @@ for (let {var1, var2} of someArr) {
     var2 = null;
 }
 
+{
+    let k: any = 0;
+    function foo(param: {[k: string]: string}) {
+        k = param;
+    }
+}
+
diff --git a/test/rules/prefer-const/default/test.ts.lint b/test/rules/prefer-const/default/test.ts.lint
@@ -258,6 +258,13 @@ for (let {var1, var2} of someArr) {
     var2 = null;
 }
 
+{
+    let k: any = 0;
+    function foo(param: {[k: string]: string}) {
+        k = param;
+    }
+}
+
 [_base]: Identifier '%%s' is never reassigned; use 'const' instead of '%s'.
 [let]: _base % ('let')
 [var]: _base % ('var')