[Issue 15309] New: [dmd-internal] ScopeExp.semantic() should set its type always

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15309

          Issue ID: 15309
           Summary: [dmd-internal] ScopeExp.semantic() should set its type
                    always
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: k.hara.pg at gmail.com

Expression.semantic should set the 'type' field when the semantic analysis
process succeeds. However ScopeExp.semantic may leave it as 'null'.  Look at
this snippet.

int foo(T, U...)(U arg) { return 0; }
void main() { auto x = foo!int;  }   // 'foo!int' is parsed as ScopeExp.

When you compile the code, it will pass a problematic code path.

    override Expression semantic(Scope* sc)
    {
        ...

        ScopeDsymbol sds2 = sds;
        TemplateInstance ti = sds2.isTemplateInstance();
        while (ti)
        {
            ...
            if (ti.needsTypeInference(sc))
            {
                if (auto td = ti.tempdecl.isTemplateDeclaration())
                {
                    ...
                }
                else if (auto os = ti.tempdecl.isOverloadSet())
                {
                    ...
                }
                /* here, this.type will leave as 'null' */
                return this;
            }
        ...

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