From 052a3d9d73a009e11f26fa8ba99f6e72c63b5e6d Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Thu, 5 Sep 2019 16:16:35 -0700
Subject: [PATCH] Infer void from expr statement usage, not calls

This makes inferences a lot better.
---
 src/services/codefixes/inferFromUsage.ts                 | 8 +++++---
 .../cases/fourslash/codeFixInferFromCallInAssignment.ts  | 9 +++++++++
 .../fourslash/codeFixInferFromExpressionStatement.ts     | 8 ++++++++
 .../codeFixInferFromUsageCommentAfterParameter.ts        | 2 +-
 tests/cases/fourslash/codeFixInferFromUsageJSXElement.ts | 2 +-
 .../fourslash/codeFixInferFromUsagePropertyAccess.ts     | 2 +-
 .../fourslash/codeFixInferFromUsagePropertyAccessJS.ts   | 2 +-
 7 files changed, 26 insertions(+), 7 deletions(-)
 create mode 100644 tests/cases/fourslash/codeFixInferFromCallInAssignment.ts
 create mode 100644 tests/cases/fourslash/codeFixInferFromExpressionStatement.ts

diff --git a/src/services/codefixes/inferFromUsage.ts b/src/services/codefixes/inferFromUsage.ts
index 0a190e7b379..daa2166103a 100644
--- a/src/services/codefixes/inferFromUsage.ts
+++ b/src/services/codefixes/inferFromUsage.ts
@@ -504,6 +504,9 @@ namespace ts.codefix {
             }
 
             switch (node.parent.kind) {
+                case SyntaxKind.ExpressionStatement:
+                    addCandidateType(usage, checker.getVoidType());
+                    break;
                 case SyntaxKind.PostfixUnaryExpression:
                     usage.isNumber = true;
                     break;
@@ -871,12 +874,11 @@ namespace ts.codefix {
                 }
 
                 if (usage.calls) {
-                    callSignatures.push(getSignatureFromCalls(usage.calls, checker.getVoidType()));
+                    callSignatures.push(getSignatureFromCalls(usage.calls, checker.getAnyType()));
                 }
 
                 if (usage.constructs) {
-                    // TODO: fallback return should maybe be {}?
-                    constructSignatures.push(getSignatureFromCalls(usage.constructs, checker.getVoidType()));
+                    constructSignatures.push(getSignatureFromCalls(usage.constructs, checker.getAnyType()));
                 }
 
                 if (usage.stringIndex) {
diff --git a/tests/cases/fourslash/codeFixInferFromCallInAssignment.ts b/tests/cases/fourslash/codeFixInferFromCallInAssignment.ts
new file mode 100644
index 00000000000..85e1d3bc509
--- /dev/null
+++ b/tests/cases/fourslash/codeFixInferFromCallInAssignment.ts
@@ -0,0 +1,9 @@
+/// <reference path='fourslash.ts' />
+
+// @noImplicitAny: true
+//// function inferAny( [| app |] ) {
+////     const result = app.use('hi')
+////     return result
+//// }
+
+verify.rangeAfterCodeFix("app: { use: (arg0: string) => any; }");
diff --git a/tests/cases/fourslash/codeFixInferFromExpressionStatement.ts b/tests/cases/fourslash/codeFixInferFromExpressionStatement.ts
new file mode 100644
index 00000000000..b5969c79378
--- /dev/null
+++ b/tests/cases/fourslash/codeFixInferFromExpressionStatement.ts
@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+// @noImplicitAny: true
+//// function inferVoid( [| app |] ) {
+////     app.use('hi')
+//// }
+
+verify.rangeAfterCodeFix("app: { use: (arg0: string) => void; }");
diff --git a/tests/cases/fourslash/codeFixInferFromUsageCommentAfterParameter.ts b/tests/cases/fourslash/codeFixInferFromUsageCommentAfterParameter.ts
index bdefd2b5dea..866bfe04c13 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageCommentAfterParameter.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageCommentAfterParameter.ts
@@ -16,7 +16,7 @@ verify.codeFix({
     index: 0,
     newFileContent:
 `/**
- * @param {(arg0: any) => void} callback
+ * @param {(arg0: any) => any} callback
  */
 function coll(callback /*, name1, name2, ... */) {
     return callback(this);
diff --git a/tests/cases/fourslash/codeFixInferFromUsageJSXElement.ts b/tests/cases/fourslash/codeFixInferFromUsageJSXElement.ts
index 3200fffafb8..abe35fe46c8 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageJSXElement.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageJSXElement.ts
@@ -30,4 +30,4 @@
 //// }
 
 
-verify.rangeAfterCodeFix("props: { isLoading: any; update: (arg0: any) => void; }",/*includeWhiteSpace*/ undefined, /*errorCode*/ undefined, 0);
+verify.rangeAfterCodeFix("props: { isLoading: any; update: (arg0: any) => any; }",/*includeWhiteSpace*/ undefined, /*errorCode*/ undefined, 0);
diff --git a/tests/cases/fourslash/codeFixInferFromUsagePropertyAccess.ts b/tests/cases/fourslash/codeFixInferFromUsagePropertyAccess.ts
index c8b85ee11e8..44d2e2d7b1c 100644
--- a/tests/cases/fourslash/codeFixInferFromUsagePropertyAccess.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsagePropertyAccess.ts
@@ -12,4 +12,4 @@
 ////    return x.y.z
 ////}
 
-verify.rangeAfterCodeFix("a: { b: { c: any; }; }, m: { n: () => number; }, x: { y: { z: number[]; }; }", /*includeWhiteSpace*/ undefined, /*errorCode*/ undefined, /*index*/0);
\ No newline at end of file
+verify.rangeAfterCodeFix("a: { b: { c: void; }; }, m: { n: () => number; }, x: { y: { z: number[]; }; }", /*includeWhiteSpace*/ undefined, /*errorCode*/ undefined, /*index*/0);
diff --git a/tests/cases/fourslash/codeFixInferFromUsagePropertyAccessJS.ts b/tests/cases/fourslash/codeFixInferFromUsagePropertyAccessJS.ts
index ed9d4b33b37..357b1a991ba 100644
--- a/tests/cases/fourslash/codeFixInferFromUsagePropertyAccessJS.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsagePropertyAccessJS.ts
@@ -21,7 +21,7 @@ verify.codeFix({
     index: 0,
     newFileContent:
 `/**
- * @param {{ b: { c: any; }; }} a
+ * @param {{ b: { c: void; }; }} a
  * @param {{ n: () => number; }} m
  * @param {{ y: { z: number[]; }; }} x
  */