Fix inferFromUsage on index signatures (microsoft#25934)

sandersn · web-flow · commit 9658b476c2fb · 2018-07-25T10:51:11.000-07:00
* Fix inferFromUsage on index signatures

1. Check the argumentExpression to determine the index signature type.
Previously, the code mistakenly checked the type of the element access
itself, which never returned a good type.
2. If inference for the index signature type fails, substitute anyType.
Previously, the code would create a bad index signature with an
undefined type.
3. Add tests. Previously, there were no tests.

* Fixing (1) means that number index signatures are now created.
Previously, only string index signatures would be created.
* Fixing (2) means that index signatures will be inferred from single
usage like `return a[0]`. Previously, the refactoring would fail,
perhaps because of a check when stringifying the index signature (I
haven't tracked down why.)

* Update fourslash test with improved inference
diff --git a/src/services/codefixes/inferFromUsage.ts b/src/services/codefixes/inferFromUsage.ts
@@ -501,7 +501,7 @@ namespace ts.codefix {
                 return;
             }
             else {
-                const indexType = checker.getTypeAtLocation(parent);
+                const indexType = checker.getTypeAtLocation(parent.argumentExpression);
                 const indexUsageContext = {};
                 inferTypeFromContext(parent, checker, indexUsageContext);
                 if (indexType.flags & TypeFlags.NumberLike) {
@@ -562,11 +562,11 @@ namespace ts.codefix {
                 }
 
                 if (usageContext.numberIndexContext) {
-                    numberIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.numberIndexContext, checker)!, /*isReadonly*/ false); // TODO: GH#18217
+                    numberIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.numberIndexContext, checker) || checker.getAnyType(), /*isReadonly*/ false);
                 }
 
                 if (usageContext.stringIndexContext) {
-                    stringIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.stringIndexContext, checker)!, /*isReadonly*/ false);
+                    stringIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.stringIndexContext, checker) || checker.getAnyType(), /*isReadonly*/ false);
                 }
 
                 return checker.createAnonymousType(/*symbol*/ undefined!, members, callSignatures, constructSignatures, stringIndexInfo, numberIndexInfo); // TODO: GH#18217
diff --git a/tests/cases/fourslash/codeFixInferFromUsageNumberIndexSignature.ts b/tests/cases/fourslash/codeFixInferFromUsageNumberIndexSignature.ts
@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+// @noImplicitAny: true
+////function f([|a |]) {
+////    return a[0] + 1;
+////}
+
+verify.rangeAfterCodeFix("a: { [x: number]: number; }",/*includeWhiteSpace*/ undefined, /*errorCode*/ undefined, 0);
diff --git a/tests/cases/fourslash/codeFixInferFromUsageStringIndexSignature.ts b/tests/cases/fourslash/codeFixInferFromUsageStringIndexSignature.ts
@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+// @noImplicitAny: true
+////function f([|a |]) {
+////    return a['hi'];
+////}
+
+verify.rangeAfterCodeFix("a: { [x: string]: any; }",/*includeWhiteSpace*/ undefined, /*errorCode*/ undefined, 0);
diff --git a/tests/cases/fourslash/typeToStringCrashInCodeFix.ts b/tests/cases/fourslash/typeToStringCrashInCodeFix.ts
@@ -1,6 +1,6 @@
 /// <reference path="fourslash.ts" />
 
 // @noImplicitAny: true
-//// function f(y, z = { p: y[
+//// function f([|y |], z = { p: y[
 
-verify.not.codeFixAvailable();
+verify.rangeAfterCodeFix("y: { [x: string]: any; }",/*includeWhiteSpace*/ undefined, /*errorCode*/ undefined, 0);

Original file line number	Diff line number	Diff line change
`@@ -501,7 +501,7 @@ namespace ts.codefix {`
`501`	`501`	`return;`
`502`	`502`	`}`
`503`	`503`	`else {`
`504`		`- const indexType = checker.getTypeAtLocation(parent);`
	`504`	`+ const indexType = checker.getTypeAtLocation(parent.argumentExpression);`
`505`	`505`	`const indexUsageContext = {};`
`506`	`506`	`inferTypeFromContext(parent, checker, indexUsageContext);`
`507`	`507`	`if (indexType.flags & TypeFlags.NumberLike) {`
`@@ -562,11 +562,11 @@ namespace ts.codefix {`
`562`	`562`	`}`
`563`	`563`
`564`	`564`	`if (usageContext.numberIndexContext) {`
`565`		`- numberIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.numberIndexContext, checker)!, /isReadonly/ false); // TODO: GH#18217`
	`565`	`+ numberIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.numberIndexContext, checker) \|\| checker.getAnyType(), /isReadonly/ false);`
`566`	`566`	`}`
`567`	`567`
`568`	`568`	`if (usageContext.stringIndexContext) {`
`569`		`- stringIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.stringIndexContext, checker)!, /isReadonly/ false);`
	`569`	`+ stringIndexInfo = checker.createIndexInfo(getTypeFromUsageContext(usageContext.stringIndexContext, checker) \|\| checker.getAnyType(), /isReadonly/ false);`
`570`	`570`	`}`
`571`	`571`
`572`	`572`	`return checker.createAnonymousType(/symbol/ undefined!, members, callSignatures, constructSignatures, stringIndexInfo, numberIndexInfo); // TODO: GH#18217`