[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

    20 files      20 suites   3d 12h 26m 33s ⏱️
 3 016 tests  3 011 ✅ 0 💤 5 ❌
58 673 runs  58 668 ✅ 0 💤 5 ❌

For more details on these failures, see this check.

Results for commit 9e986fa.

♻️ This comment has been updated with latest results.

[dpiparo]

CC: @silverweed

[vgvassilev]

Lgtm, if we add a test in clingtest.

[dpiparo]

@devajithvs do you think we can follow @hahnjo suggestion to move on, merge and close the associated issue?

[devajithvs]

Done! The test is indeed very brittle and can break based on where // expected-error goes.

eg,

p.q // expected-error@input_line_28:2 {{use of undeclared identifier 'p'}}

will fail.

[dpiparo]

Thanks. The errors on mac14 seem unrelated.