ambiguous identifier resolution (#23123)

fixes #23002, fixes #22841, refs comments in #23097

When an identifier is ambiguous in scope (i.e. multiple imports contain
symbols with the same name), attempt resolving it through type inference
(by creating a symchoice). To do this efficiently, `qualifiedLookUp` had
to be broken up so that `semExpr` can access the ambiguous candidates
directly (now obtained directly via `lookUpCandidates`).

This fixes the linked issues, but an example like:

```nim
let on = 123

{.warning[ProveInit]: on.}
```

will still fail, since `on` is unambiguously the local `let` symbol here
(this is also true for `proc on` but `proc` symbols generate symchoices
anyway).

Type symbols are not considered to not confuse the type inference. This
includes the change in sigmatch, up to this point symchoices with
nonoverloadable symbols could be created, they just wouldn't be
considered during disambiguation. Now every proper symbol except types
are considered in disambiguation, so the correct symbols must be picked
during the creation of the symchoice node. I remember there being a
violating case of this in the compiler, but this was very likely fixed
by excluding type symbols as CI seems to have found no issues.

The pure enum ambiguity test was disabled because ambiguous pure enums
now behave like overloadable enums with this behavior, so we get a
longer error message for `echo amb` like `type mismatch: got <MyEnum |
OtherEnum> but expected T`

10 files changed, 32 insertions, 8 deletions

diff --git a/tests/enum/tambiguousoverloads.nim b/tests/enum/tambiguousoverloads.nim
index aa75eaa91..12c78c848 100644
--- a/tests/enum/tambiguousoverloads.nim
+++ b/tests/enum/tambiguousoverloads.nim
@@ -9,7 +9,7 @@ block: # bug #21887
     EnumC = enum C
 
   doAssert typeof(EnumC(A)) is EnumC #[tt.Error
-                        ^ ambiguous identifier 'A' -- use one of the following:
+                        ^ ambiguous identifier: 'A' -- use one of the following:
   EnumA.A: EnumA
   EnumB.A: EnumB]#
 
@@ -21,6 +21,6 @@ block: # issue #22598
       red
 
   let a = red #[tt.Error
-          ^ ambiguous identifier 'red' -- use one of the following:
+          ^ ambiguous identifier: 'red' -- use one of the following:
   A.red: A
   B.red: B]#
diff --git a/tests/enum/tpure_enums_conflict.nim b/tests/enum/tpure_enums_conflict.nim
index 3c7528a72..4411fd2a6 100644
--- a/tests/enum/tpure_enums_conflict.nim
+++ b/tests/enum/tpure_enums_conflict.nim
@@ -1,4 +1,5 @@
 discard """
+  disabled: true # pure enums behave like overloaded enums on ambiguity now which gives a different error message
   errormsg: "ambiguous identifier: 'amb'"
   line: 19
 """
diff --git a/tests/errmsgs/t8064.nim b/tests/errmsgs/t8064.nim
index 6be83fd1a..c35a3abcc 100644
--- a/tests/errmsgs/t8064.nim
+++ b/tests/errmsgs/t8064.nim
@@ -5,5 +5,5 @@ values
 
 discard """
   # either this or "expression has no type":
-  errormsg: "ambiguous identifier 'values' -- use one of the following:"
+  errormsg: "ambiguous identifier: 'values' -- use one of the following:"
 """
diff --git a/tests/lookups/tambiguousemit.nim b/tests/lookups/tambiguousemit.nim
index 0ebd0a255..4f4bacce4 100644
--- a/tests/lookups/tambiguousemit.nim
+++ b/tests/lookups/tambiguousemit.nim
@@ -7,6 +7,6 @@ proc foo(x: int) = discard
 proc foo(x: float) = discard
 
 {.emit: ["// ", foo].} #[tt.Error
-                ^ ambiguous identifier 'foo' -- use one of the following:
+                ^ ambiguous identifier: 'foo' -- use one of the following:
   tambiguousemit.foo: proc (x: int){.noSideEffect, gcsafe.}
   tambiguousemit.foo: proc (x: float){.noSideEffect, gcsafe.}]#
diff --git a/tests/lookups/tambprocvar.nim b/tests/lookups/tambprocvar.nim
index 33323fbb2..f5c3fde4f 100644
--- a/tests/lookups/tambprocvar.nim
+++ b/tests/lookups/tambprocvar.nim
@@ -2,7 +2,7 @@ discard """
   action: reject
   cmd: "nim check $file"
   nimout: '''
-tambprocvar.nim(15, 11) Error: ambiguous identifier 'foo' -- use one of the following:
+tambprocvar.nim(15, 11) Error: ambiguous identifier: 'foo' -- use one of the following:
   tambprocvar.foo: proc (x: int){.noSideEffect, gcsafe.}
   tambprocvar.foo: proc (x: float){.noSideEffect, gcsafe.}
 '''
@@ -16,4 +16,4 @@ block:
 
 block:
   let x = `+` #[tt.Error
-           ^ ambiguous identifier '+' -- use one of the following:]#
+          ^ ambiguous identifier: '+' -- use one of the following:]#
diff --git a/tests/lookups/tambsym3.nim b/tests/lookups/tambsym3.nim
index 6e7589cd8..6bbebca10 100644
--- a/tests/lookups/tambsym3.nim
+++ b/tests/lookups/tambsym3.nim
@@ -1,5 +1,5 @@
 discard """
-  errormsg: "ambiguous identifier 'mDec' -- use one of the following:"
+  errormsg: "ambiguous identifier: 'mDec' -- use one of the following:"
   file: "tambsym3.nim"
   line: 11
 """
diff --git a/tests/macros/t23032_2.nim b/tests/macros/t23032_2.nim
index cb8e772e7..8dde29e10 100644
--- a/tests/macros/t23032_2.nim
+++ b/tests/macros/t23032_2.nim
@@ -1,6 +1,6 @@
 discard """
   action: "reject"
-  errormsg: "ambiguous identifier '%*'"
+  errormsg: "ambiguous identifier: '%*'"
 """
 import std/macros
 
diff --git a/tests/pragmas/monoff1.nim b/tests/pragmas/monoff1.nim
new file mode 100644
index 000000000..85d6c57b3
--- /dev/null
+++ b/tests/pragmas/monoff1.nim
@@ -0,0 +1 @@
+proc on*() = discard
diff --git a/tests/pragmas/tonoff1.nim b/tests/pragmas/tonoff1.nim
new file mode 100644
index 000000000..20ba7def2
--- /dev/null
+++ b/tests/pragmas/tonoff1.nim
@@ -0,0 +1,8 @@
+# issue #23002
+
+import monoff1
+
+proc test() =
+  {.warning[ProveInit]: on.}
+
+test()
diff --git a/tests/pragmas/tonoff2.nim b/tests/pragmas/tonoff2.nim
new file mode 100644
index 000000000..9dff5ef11
--- /dev/null
+++ b/tests/pragmas/tonoff2.nim
@@ -0,0 +1,14 @@
+discard """
+    action: compile
+"""
+
+# issue #22841
+
+import unittest
+
+proc on() =
+    discard
+
+suite "some suite":
+    test "some test":
+        discard