[cling] Emit proper diagnostics in DynamicLookup for AutoType

[devajithvs]

Replace AST dumps with proper error messages in dynamic lookup when dealing with auto, which is unsupported for lookup

Changes this:

root [0] auto var = someexpr();
ROOT_prompt_0:1:1: error: Syntax error
auto var = someexpr();
^
FunctionDecl 0x60cb530887f0 <input_line_8:1:1, ROOT_prompt_0:3:1> input_line_8:1:6 __cling_Un1Qu30 'void (void *)'
|-ParmVarDecl 0x60cb53088738 <col:22, col:28> col:28 vpClingValue 'void *'
|-CompoundStmt 0x60cb53088c30 <col:42, ROOT_prompt_0:3:1>
| |-DeclStmt 0x60cb53088c10 <line:1:1, col:22>
| | `-VarDecl 0x60cb53088910 <col:1, col:21> col:6 var 'auto' cinit
| |   `-CallExpr 0x60cb53088bc0 <col:12, col:21> '<dependent type>'
| |     `-DeclRefExpr 0x60cb53088b80 <col:12> '<dependent type>' lvalue Var 0x60cb53088aa8 'someexpr' '<dependent type>'
| `-NullStmt 0x60cb53088c28 <line:2:1>
|-AnnotateAttr 0x60cb53088a00 <<invalid sloc>> Implicit R"ATTRDUMP(__ResolveAtRuntime)ATTRDUMP"
`-AnnotateAttr 0x60cb53088b10 <<invalid sloc>> Implicit R"ATTRDUMP(__ResolveAtRuntime)ATTRDUMP"
<<<NULL>>>

to

root [0] auto var = someexpr();
ROOT_prompt_0:1:12: error: Cannot deduce 'auto' from unknown expression
auto var = someexpr();
           ^

This Pull request:

Changes or fixes:

Checklist:

• tested changes locally
• updated the docs (if necessary)

Fixes #9261

CC: @guitargeek

[github-actions]

Test Results

    18 files      18 suites   4d 22h 33m 13s ⏱️
 2 737 tests  2 735 ✅ 0 💤 2 ❌
47 733 runs  47 731 ✅ 0 💤 2 ❌

For more details on these failures, see this check.

Results for commit 9292714.

♻️ This comment has been updated with latest results.

[dpiparo]

CC: @silverweed

[vgvassilev]

Lgtm, if we add a test in clingtest.

[vgvassilev]

What about adding -verify and //expected-error?

[devajithvs]

If we have -verify, we would have to change that for p.q too, I tried to do something like

p.q // expected-error {{use of undeclared identifier 'p'}}

// `auto` is not supported
auto x = unknownexpression(); // expected-error {{cannot deduce 'auto' from unknown expression}}

But I get this (the string is the exact same, but the line number is different)

error: 'expected-error' diagnostics expected but not seen: 
  File input_line_27 Line 2: use of undeclared identifier 'p'
error: 'expected-error' diagnostics seen but not expected: 
  File input_line_28 Line 2: use of undeclared identifier 'p'

[vgvassilev]

You can check how the other diag checks are done in the tests. There is syntax for it although what you wrote should have worked

[dpiparo]

Is there a combination that guarantees coverage and works? We need pragmatism... It would be nice to have this fixed asap :)

[hahnjo]

As far as I understand, the file used FileCheck before. I agree it would be nice to use -verify, but I've seen other cases in the past where it was hard because of Cling line errors... Maybe this is one of the cases where you have to give the exact line number as // expected-error@input_line_28 {{cannot deduce 'auto' from unknown expression}} (and then sometimes suffer updating the line numbers when changing the test)