fix(49200): skip duplicated method declarations (#50609)

Author: a-tarasyuk

src/compiler/checker.ts

@@ -7280,6 +7280,7 @@ namespace ts {
                         && symbol.escapedName !== InternalSymbolName.ExportEquals
                         && !(symbol.flags & SymbolFlags.Prototype)
                         && !(symbol.flags & SymbolFlags.Class)
+                        && !(symbol.flags & SymbolFlags.Method)
                         && !isConstMergedWithNSPrintableAsSignatureMerge) {
                         if (propertyAsAlias) {
                             const createdExport = serializeMaybeAliasAssignment(symbol);

tests/baselines/reference/declarationEmitMethodDeclaration.js

@@ -0,0 +1,17 @@
+//// [a.js]
+export default {
+    methods: {
+        foo() { }
+    }
+}
+
+
+
+
+//// [a.d.ts]
+declare namespace _default {
+    namespace methods {
+        function foo(): void;
+    }
+}
+export default _default;

tests/baselines/reference/declarationEmitMethodDeclaration.symbols

@@ -0,0 +1,10 @@
+=== /a.js ===
+export default {
+    methods: {
+>methods : Symbol(methods, Decl(a.js, 0, 16))
+
+        foo() { }
+>foo : Symbol(foo, Decl(a.js, 1, 14))
+    }
+}
+

tests/baselines/reference/declarationEmitMethodDeclaration.types

@@ -0,0 +1,13 @@
+=== /a.js ===
+export default {
+>{    methods: {        foo() { }    }} : { methods: { foo(): void; }; }
+
+    methods: {
+>methods : { foo(): void; }
+>{        foo() { }    } : { foo(): void; }
+
+        foo() { }
+>foo : () => void
+    }
+}
+

tests/cases/compiler/declarationEmitMethodDeclaration.ts

@@ -0,0 +1,10 @@
+// @allowJs: true
+// @checkJs: true
+// @declaration: true
+// @emitDeclarationOnly: true
+// @filename: /a.js
+export default {
+    methods: {
+        foo() { }
+    }
+}