add a source location for GenericTypeParamDecls (#64722)

rdar://105982860

Author: QuietMisdreavus

lib/AST/NameLookup.cpp

@@ -3050,7 +3050,8 @@ createOpaqueParameterGenericParams(GenericContext *genericContext, GenericParamL
       // Allocate a new generic parameter to represent this opaque type.
       auto *gp = GenericTypeParamDecl::createImplicit(
           dc, Identifier(), GenericTypeParamDecl::InvalidDepth, index++,
-          /*isParameterPack*/ false, /*isOpaqueType*/ true, repr);
+          /*isParameterPack*/ false, /*isOpaqueType*/ true, repr,
+          /*nameLoc*/ repr->getStartLoc());
 
       // Use the underlying constraint as the constraint on the generic parameter.
       //  The underlying constraint is only present for OpaqueReturnTypeReprs

test/SymbolGraph/Symbols/OpaqueParams.swift

@@ -0,0 +1,15 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -swift-version 5 %s -emit-module -emit-module-path %t/OpaqueParams.swiftmodule -emit-symbol-graph -emit-symbol-graph-dir %t/
+// RUN: %{python} -m json.tool %t/OpaqueParams.symbols.json %t/OpaqueParams.formatted.symbols.json
+// RUN: %FileCheck %s --input-file %t/OpaqueParams.formatted.symbols.json
+
+// CHECK: "precise": "s:12OpaqueParams7MyClassC6myFunc5param10otherParamyq__xtAA0C8ProtocolRzAaGR_r0_lF"
+
+public protocol MyProtocol {}
+
+public class MyClass {
+    public func myFunc<S: MyProtocol>(
+        param: some MyProtocol,
+        otherParam: S
+    ) {}
+}