REPL: Show input alias (e.g., \\:cat:) for Char display

NEWS.md

@@ -62,6 +62,8 @@ Standard library changes
 
 #### REPL
 
+* The display of `AbstractChar`s in the main REPL mode now includes LaTeX input information like what is shown in help mode ([#58181]).
+
 #### Test
 
 * Test failures when using the `@test` macro now show evaluated arguments for all function calls ([#57825], [#57839]).

stdlib/REPL/src/REPL.jl

@@ -555,6 +555,16 @@ display(d::REPLDisplay, x) = display(d, MIME("text/plain"), x)
 
 show_repl(io::IO, mime::MIME"text/plain", x) = show(io, mime, x)
 
+function show_repl(io::IO, mime::MIME"text/plain", c::AbstractChar)
+    show(io, mime, c) # Call the original Base.show
+    # Check for LaTeX/emoji alias and print if found and using symbol_latex which is used in help?> mode
+    latex = symbol_latex(string(c))
+    if !isempty(latex)
+        print(io, ", input as ")
+        printstyled(io, latex, "<tab>"; color=:cyan)
+    end
+end
+
 show_repl(io::IO, ::MIME"text/plain", ex::Expr) =
     print(io, JuliaSyntaxHighlighting.highlight(
         sprint(show, ex, context=IOContext(io, :color => false))))

stdlib/REPL/test/repl.jl

@@ -1999,3 +1999,32 @@ end
     write(proj_file, "name = \"Bar\"\n")
     @test get_prompt("--project=$proj_file") == "(Bar) pkg> "
 end
+
+# Issue #58158 add alias for Char display in REPL
+@testset "REPL show_repl Char alias" begin
+    # Test character with a known emoji alias
+    output = sprint(REPL.show_repl, MIME("text/plain"), '😼'; context=(:color => true))
+    # Check for base info and the specific alias
+    @test occursin("'😼': Unicode U+1F63C (category So: Symbol, other)", output)
+    @test occursin(", input as ", output) # Check for the prefix text
+    @test occursin("\\:smirk_cat:<tab>", output) # Check for the alias text (may be colored)
+
+    # Test character with a known LaTeX alias
+    output = sprint(REPL.show_repl, MIME("text/plain"), 'α'; context=(:color => true))
+    # Check for base info and the specific alias
+    @test occursin("'α': Unicode U+03B1 (category Ll: Letter, lowercase)", output)
+    @test occursin(", input as ", output) # Check for the prefix text
+    @test occursin("\\alpha<tab>", output) # Check for the alias text (may be colored)
+
+    # Test character without an alias
+    output = sprint(REPL.show_repl, MIME("text/plain"), 'X'; context=(:color => true))
+    # Check for base info only
+    @test occursin("'X': ASCII/Unicode U+0058 (category Lu: Letter, uppercase)", output)
+    # Ensure alias part is *not* printed
+    @test !occursin(", input as ", output)
+
+    # Test another character without an alias (symbol)
+    output = sprint(REPL.show_repl, MIME("text/plain"), '+'; context=(:color => true))
+    @test occursin("'+': ASCII/Unicode U+002B (category Sm: Symbol, math)", output)
+    @test !occursin(", input as ", output)
+end