add compile error test for invalid enum literal implicit cast

See #683

Author: andrewrk

src/ir.cpp

@@ -11601,8 +11601,10 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
 
         TypeEnumField *field = find_enum_type_field(wanted_type, value->value.data.x_enum_literal);
         if (field == nullptr) {
-            ir_add_error(ira, source_instr, buf_sprintf("enum '%s' has no field named '%s'",
+            ErrorMsg *msg = ir_add_error(ira, source_instr, buf_sprintf("enum '%s' has no field named '%s'",
                     buf_ptr(&wanted_type->name), buf_ptr(value->value.data.x_enum_literal)));
+            add_error_note(ira->codegen, msg, wanted_type->data.enumeration.decl_node,
+                    buf_sprintf("'%s' declared here", buf_ptr(&wanted_type->name)));
             return ira->codegen->invalid_instruction;
         }
         IrInstruction *result = ir_const(ira, source_instr, wanted_type);

test/compile_errors.zig

@@ -2,6 +2,20 @@ const tests = @import("tests.zig");
 const builtin = @import("builtin");
 
 pub fn addCases(cases: *tests.CompileErrorContext) void {
+    cases.add(
+        "cast enum literal to enum but it doesn't match",
+        \\const Foo = enum {
+        \\    a,
+        \\    b,
+        \\};
+        \\export fn entry() void {
+        \\    const x: Foo = .c;
+        \\}
+    ,
+        "tmp.zig:6:20: error: enum 'Foo' has no field named 'c'",
+        "tmp.zig:1:13: note: 'Foo' declared here",
+    );
+
     cases.add(
         "discarding error value",
         \\export fn entry() void {