fix #13524: magics with untyped params (eg astToStr) now work inside generics

Author: timotheecour

compiler/semgnrc.nim

@@ -226,7 +226,14 @@ proc semGenericStmt(c: PContext, n: PNode,
     var mixinContext = false
     if s != nil:
       incl(s.flags, sfUsed)
-      mixinContext = s.magic in {mDefined, mDefinedInScope, mCompiles}
+      # more robust/future proof than:
+      # mixinContext = s.magic in {mDefined, mDefinedInScope, mCompiles, mAstToStr}
+      if s.magic != mNone and s.typ != nil:
+        for i in 1..<s.typ.len:
+          if s.typ[i].kind == tyUntyped:
+            mixinContext = true
+            break
+
       let sc = symChoice(c, fn, s, if s.isMixedIn: scForceOpen else: scOpen)
       case s.kind
       of skMacro:
@@ -283,6 +290,10 @@ proc semGenericStmt(c: PContext, n: PNode,
     # is not exported and yet the generic 'threadProcWrapper' works correctly.
     let flags = if mixinContext: flags+{withinMixin} else: flags
     for i in first..<result.safeLen:
+      let flags = if mixinContext: flags+{withinMixin} else: flags
+      # instead, would be better to only set `withinMixin` for arguments of
+      # kind tyUntyped, eg `if s.typ[i].kind == tyUntyped:`, however, this
+      # currentl doesn't work
       result[i] = semGenericStmt(c, result[i], flags, ctx)
   of nkCurlyExpr:
     result = newNodeI(nkCall, n.info)

lib/system.nim

@@ -1629,7 +1629,7 @@ else:
       result[i+1] = y[i]
 
 
-proc astToStr*[T](x: T): string {.magic: "AstToStr", noSideEffect.}
+proc astToStr*(x: untyped): string {.magic: "AstToStr", noSideEffect.}
   ## Converts the AST of `x` into a string representation. This is very useful
   ## for debugging.
 

tests/generics/t13525.nim

@@ -0,0 +1,6 @@
+# https://github.com/nim-lang/Nim/issues/13524
+template fun(field): untyped = astToStr(field)
+proc test1(): string = fun(nonexistant1)
+proc test2[T](): string = fun(nonexistant2) # used to cause: Error: undeclared identifier: 'nonexistant2'
+doAssert test1() == "nonexistant1"
+doAssert test2[int]() == "nonexistant2"