Properly reduce intersections of string literal and template literal …

…types (#41162) * Properly reduce single element intersections * Add regression test * Accept new baselines
microsoft · Oct 19, 2020 · 4638c68 · 4638c68
1 parent 15cec9d
commit 4638c68
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Showing 6 changed files with 43 additions and 9 deletions.
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -13373,6 +13373,9 @@ namespace ts {
                 includes & TypeFlags.VoidLike && includes & (TypeFlags.DisjointDomains & ~TypeFlags.VoidLike)) {
                 return neverType;
             }
+            if (includes & TypeFlags.TemplateLiteral && includes & TypeFlags.StringLiteral && extractRedundantTemplateLiterals(typeSet)) {
+                return neverType;
+            }
             if (includes & TypeFlags.Any) {
                 return includes & TypeFlags.IncludesWildcard ? wildcardType : anyType;
             }
@@ -13424,12 +13427,7 @@ namespace ts {
                     }
                 }
                 else {
-                    if (includes & TypeFlags.TemplateLiteral && includes & TypeFlags.StringLiteral && extractRedundantTemplateLiterals(typeSet)) {
-                        result = neverType;
-                    }
-                    else {
-                        result = createIntersectionType(typeSet, aliasSymbol, aliasTypeArguments);
-                    }
+                    result = createIntersectionType(typeSet, aliasSymbol, aliasTypeArguments);
                 }
                 intersectionTypes.set(id, result);
             }

diff --git a/tests/baselines/reference/templateLiteralTypesPatterns.errors.txt b/tests/baselines/reference/templateLiteralTypesPatterns.errors.txt
@@ -332,4 +332,10 @@ tests/cases/conformance/types/literal/templateLiteralTypesPatterns.ts(160,7): er
     const exampleBad: B = "anything"; // fails
           ~~~~~~~~~~
 !!! error TS2322: Type '"anything"' is not assignable to type '`${number} ${number}`'.
-    const exampleGood: B = "1 2"; // ok
+    const exampleGood: B = "1 2"; // ok
+
+    // Repro from #41161
+
+    var aa: '0';
+    var aa: '0' & `${number}`;
+
diff --git a/tests/baselines/reference/templateLiteralTypesPatterns.js b/tests/baselines/reference/templateLiteralTypesPatterns.js
@@ -159,7 +159,13 @@ const shouldWork2: AGen<string> = null as any as AGen<number>;
 type A = `${number}`;
 type B = `${A} ${A}`;
 const exampleBad: B = "anything"; // fails
-const exampleGood: B = "1 2"; // ok
+const exampleGood: B = "1 2"; // ok
+
+// Repro from #41161
+
+var aa: '0';
+var aa: '0' & `${number}`;
+
 
 //// [templateLiteralTypesPatterns.js]
 "use strict";
@@ -280,3 +286,6 @@ var shouldWork1 = null;
 var shouldWork2 = null;
 var exampleBad = "anything"; // fails
 var exampleGood = "1 2"; // ok
+// Repro from #41161
+var aa;
+var aa;
diff --git a/tests/baselines/reference/templateLiteralTypesPatterns.symbols b/tests/baselines/reference/templateLiteralTypesPatterns.symbols
@@ -393,3 +393,11 @@ const exampleGood: B = "1 2"; // ok
 >exampleGood : Symbol(exampleGood, Decl(templateLiteralTypesPatterns.ts, 160, 5))
 >B : Symbol(B, Decl(templateLiteralTypesPatterns.ts, 157, 21))
 
+// Repro from #41161
+
+var aa: '0';
+>aa : Symbol(aa, Decl(templateLiteralTypesPatterns.ts, 164, 3), Decl(templateLiteralTypesPatterns.ts, 165, 3))
+
+var aa: '0' & `${number}`;
+>aa : Symbol(aa, Decl(templateLiteralTypesPatterns.ts, 164, 3), Decl(templateLiteralTypesPatterns.ts, 165, 3))
+
diff --git a/tests/baselines/reference/templateLiteralTypesPatterns.types b/tests/baselines/reference/templateLiteralTypesPatterns.types
@@ -552,3 +552,11 @@ const exampleGood: B = "1 2"; // ok
 >exampleGood : `${number} ${number}`
 >"1 2" : "1 2"
 
+// Repro from #41161
+
+var aa: '0';
+>aa : "0"
+
+var aa: '0' & `${number}`;
+>aa : "0"
+
diff --git a/tests/cases/conformance/types/literal/templateLiteralTypesPatterns.ts b/tests/cases/conformance/types/literal/templateLiteralTypesPatterns.ts
@@ -159,4 +159,9 @@ const shouldWork2: AGen<string> = null as any as AGen<number>;
 type A = `${number}`;
 type B = `${A} ${A}`;
 const exampleBad: B = "anything"; // fails
-const exampleGood: B = "1 2"; // ok
+const exampleGood: B = "1 2"; // ok
+
+// Repro from #41161
+
+var aa: '0';
+var aa: '0' & `${number}`;