Show variable names and remove spurious type warning in typed ast.

Fixes #15714

Author: yuyichao

base/interactiveutil.jl

@@ -237,7 +237,8 @@ function code_warntype(io::IO, f, t::ANY)
         print(emph_io, "\nBody:\n  ")
         body = Expr(:body); body.args = uncompressed_ast(li)
         body.typ = li.rettype
-        show_unquoted(emph_io, body, 2)
+        # Fix slot names and types in function body
+        show_unquoted(IOContext(emph_io, :LAMBDAINFO => li), body, 2)
         print(emph_io, '\n')
     end
     nothing

base/show.jl

@@ -210,9 +210,11 @@ end
 
 function show(io::IO, l::LambdaInfo)
     println(io, "LambdaInfo for ", l.name)
+    # Fix slot names and types in function body
+    lambda_io = IOContext(io, :LAMBDAINFO => l)
     body = Expr(:body); body.args = uncompressed_ast(l)
     body.typ = l.rettype
-    show(io, body)
+    show(lambda_io, body)
 end
 
 function show_delim_array(io::IO, itr::Union{AbstractArray,SimpleVector}, op, delim, cl, delim_one,
@@ -496,10 +498,33 @@ show_unquoted(io::IO, ex::TopNode, ::Int, ::Int)        = print(io,"top(",ex.nam
 show_unquoted(io::IO, ex::GlobalRef, ::Int, ::Int)      = print(io, ex.mod, '.', ex.name)
 
 function show_unquoted(io::IO, ex::Slot, ::Int, ::Int)
-    print(io, "_", ex.id)
+    li = get(io, :LAMBDAINFO, false)
+    typ = ex.typ
+    slotid = ex.id
+    name_printed = false
+    if isa(li, LambdaInfo)
+        li = li::LambdaInfo
+        slotnames = li.slotnames
+        if isa(slotnames, Array) && slotid <= length(slotnames::Array)
+            name = li.slotnames[slotid]
+            if name !== symbol("#temp#")
+                print(io, name)
+                name_printed = true
+            end
+        end
+        slottypes = li.slottypes
+        if isa(slottypes, Array) && slotid <= length(slottypes::Array)
+            slottype = li.slottypes[slotid]
+            # The Slot in assignment can somehow have a Any type
+            slottype <: typ && (typ = slottype)
+        end
+    end
+    if !name_printed
+        print(io, "_", slotid)
+    end
     emphstate = typeemphasize(io)
-    if emphstate || ex.typ !== Any
-        show_expr_type(io, ex.typ, emphstate)
+    if emphstate || typ !== Any
+        show_expr_type(io, typ, emphstate)
     end
 end
 

test/reflection.jl

@@ -278,3 +278,35 @@ let
     @test methods(m,Tuple{Int, Int})[1]==@which MacroTest.@macrotest 1 1
     @test functionloc(@which @macrotest 1 1) == @functionloc @macrotest 1 1
 end
+
+# issue #15714
+# show variable names for slots and suppress spurious type warnings
+function f15714(array_var15714)
+    for index_var15714 in eachindex(array_var15714)
+        array_var15714[index_var15714] += 0
+    end
+end
+
+let str, li = code_typed(f15714, Tuple{Vector{Float32}})[1]
+    for str in (sprint(io->code_warntype(io, f15714, Tuple{Vector{Float32}})),
+                sprint(io->show(io, li)))
+        @test contains(str, "index_var15714")
+        @test contains(str, "array_var15714")
+        @test !contains(str, "Any")
+        @test !contains(str, "ANY")
+        # Check that we are not printing the bare slot numbers
+        for i in 1:length(li.slotnames)
+            if li.slotnames[i] === symbol("#temp#")
+                # Compiler temporaries show as slot number
+                # This assumes none of the temporaries are eliminated, which
+                # is at least true for this case.
+                @test contains(str, "_$i")
+            else
+                # Normal variables show as name
+                @test !contains(str, "_$i")
+            end
+        end
+    end
+    # Make sure printing an AST outside LambdaInfo still works.
+    show(IOBuffer(), Base.uncompressed_ast(code_typed(f15714, Tuple{Vector{Float32}})[1]))
+end