From 3885e3fcda213ec8c5f21849d6b8ddf8a5357fa7 Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wewigham@microsoft.com>
Date: Tue, 14 May 2019 16:58:06 -0700
Subject: [PATCH] Fix error message regressed by #30916 (#31276)

---
 src/compiler/checker.ts                       | 20 +++++++++++++++----
 ...gningFunctionToTupleIssuesError.errors.txt |  8 ++++++++
 .../assigningFunctionToTupleIssuesError.js    |  6 ++++++
 ...ssigningFunctionToTupleIssuesError.symbols |  8 ++++++++
 .../assigningFunctionToTupleIssuesError.types |  8 ++++++++
 .../assigningFunctionToTupleIssuesError.ts    |  2 ++
 6 files changed, 48 insertions(+), 4 deletions(-)
 create mode 100644 tests/baselines/reference/assigningFunctionToTupleIssuesError.errors.txt
 create mode 100644 tests/baselines/reference/assigningFunctionToTupleIssuesError.js
 create mode 100644 tests/baselines/reference/assigningFunctionToTupleIssuesError.symbols
 create mode 100644 tests/baselines/reference/assigningFunctionToTupleIssuesError.types
 create mode 100644 tests/cases/compiler/assigningFunctionToTupleIssuesError.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 9a64dce125591..0f18afa77410c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -12290,7 +12290,7 @@ namespace ts {
             let depth = 0;
             let expandingFlags = ExpandingFlags.None;
             let overflow = false;
-            let suppressNextError = false;
+            let overrideNextErrorInfo: DiagnosticMessageChain | undefined;
 
             Debug.assert(relation !== identityRelation || !errorNode, "no error reporting in identity checking");
 
@@ -12571,10 +12571,14 @@ namespace ts {
                 }
 
                 if (!result && reportErrors) {
-                    const maybeSuppress = suppressNextError;
-                    suppressNextError = false;
+                    let maybeSuppress = overrideNextErrorInfo;
+                    overrideNextErrorInfo = undefined;
                     if (source.flags & TypeFlags.Object && target.flags & TypeFlags.Object) {
+                        const currentError = errorInfo;
                         tryElaborateArrayLikeErrors(source, target, reportErrors);
+                        if (errorInfo !== currentError) {
+                            maybeSuppress = errorInfo;
+                        }
                     }
                     if (source.flags & TypeFlags.Object && target.flags & TypeFlags.Primitive) {
                         tryElaborateErrorsForPrimitivesAndObjects(source, target);
@@ -13506,9 +13510,10 @@ namespace ts {
                 if (unmatchedProperty) {
                     if (reportErrors) {
                         const props = arrayFrom(getUnmatchedProperties(source, target, requireOptionalProperties, /*matchDiscriminantProperties*/ false));
+                        let shouldSkipElaboration = false;
                         if (!headMessage || (headMessage.code !== Diagnostics.Class_0_incorrectly_implements_interface_1.code &&
                             headMessage.code !== Diagnostics.Class_0_incorrectly_implements_class_1_Did_you_mean_to_extend_1_and_inherit_its_members_as_a_subclass.code)) {
-                            suppressNextError = true; // Retain top-level error for interface implementing issues, otherwise omit it
+                            shouldSkipElaboration = true; // Retain top-level error for interface implementing issues, otherwise omit it
                         }
                         if (props.length === 1) {
                             const propName = symbolToString(unmatchedProperty);
@@ -13516,6 +13521,9 @@ namespace ts {
                             if (length(unmatchedProperty.declarations)) {
                                 associateRelatedInfo(createDiagnosticForNode(unmatchedProperty.declarations[0], Diagnostics._0_is_declared_here, propName));
                             }
+                            if (shouldSkipElaboration) {
+                                overrideNextErrorInfo = errorInfo;
+                            }
                         }
                         else if (tryElaborateArrayLikeErrors(source, target, /*reportErrors*/ false)) {
                             if (props.length > 5) { // arbitrary cutoff for too-long list form
@@ -13524,7 +13532,11 @@ namespace ts {
                             else {
                                 reportError(Diagnostics.Type_0_is_missing_the_following_properties_from_type_1_Colon_2, typeToString(source), typeToString(target), map(props, p => symbolToString(p)).join(", "));
                             }
+                            if (shouldSkipElaboration) {
+                                overrideNextErrorInfo = errorInfo;
+                            }
                         }
+                        // ELSE: No array like or unmatched property error - just issue top level error (errorInfo = undefined)
                     }
                     return Ternary.False;
                 }
diff --git a/tests/baselines/reference/assigningFunctionToTupleIssuesError.errors.txt b/tests/baselines/reference/assigningFunctionToTupleIssuesError.errors.txt
new file mode 100644
index 0000000000000..ca1af66c0873c
--- /dev/null
+++ b/tests/baselines/reference/assigningFunctionToTupleIssuesError.errors.txt
@@ -0,0 +1,8 @@
+tests/cases/compiler/assigningFunctionToTupleIssuesError.ts(2,5): error TS2322: Type '() => void' is not assignable to type '[string]'.
+
+
+==== tests/cases/compiler/assigningFunctionToTupleIssuesError.ts (1 errors) ====
+    declare let a: () => void;
+    let b: [string] = a;
+        ~
+!!! error TS2322: Type '() => void' is not assignable to type '[string]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assigningFunctionToTupleIssuesError.js b/tests/baselines/reference/assigningFunctionToTupleIssuesError.js
new file mode 100644
index 0000000000000..3de3da7b3cc41
--- /dev/null
+++ b/tests/baselines/reference/assigningFunctionToTupleIssuesError.js
@@ -0,0 +1,6 @@
+//// [assigningFunctionToTupleIssuesError.ts]
+declare let a: () => void;
+let b: [string] = a;
+
+//// [assigningFunctionToTupleIssuesError.js]
+var b = a;
diff --git a/tests/baselines/reference/assigningFunctionToTupleIssuesError.symbols b/tests/baselines/reference/assigningFunctionToTupleIssuesError.symbols
new file mode 100644
index 0000000000000..7a499662aeffb
--- /dev/null
+++ b/tests/baselines/reference/assigningFunctionToTupleIssuesError.symbols
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/assigningFunctionToTupleIssuesError.ts ===
+declare let a: () => void;
+>a : Symbol(a, Decl(assigningFunctionToTupleIssuesError.ts, 0, 11))
+
+let b: [string] = a;
+>b : Symbol(b, Decl(assigningFunctionToTupleIssuesError.ts, 1, 3))
+>a : Symbol(a, Decl(assigningFunctionToTupleIssuesError.ts, 0, 11))
+
diff --git a/tests/baselines/reference/assigningFunctionToTupleIssuesError.types b/tests/baselines/reference/assigningFunctionToTupleIssuesError.types
new file mode 100644
index 0000000000000..6c7d57f8483f2
--- /dev/null
+++ b/tests/baselines/reference/assigningFunctionToTupleIssuesError.types
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/assigningFunctionToTupleIssuesError.ts ===
+declare let a: () => void;
+>a : () => void
+
+let b: [string] = a;
+>b : [string]
+>a : () => void
+
diff --git a/tests/cases/compiler/assigningFunctionToTupleIssuesError.ts b/tests/cases/compiler/assigningFunctionToTupleIssuesError.ts
new file mode 100644
index 0000000000000..befea50f81d94
--- /dev/null
+++ b/tests/cases/compiler/assigningFunctionToTupleIssuesError.ts
@@ -0,0 +1,2 @@
+declare let a: () => void;
+let b: [string] = a;
\ No newline at end of file