top-level: allow analysis entry point to be specified by name (#641)

When `analyze_from_definitions` is specified as `name::Symbol`, JET
starts its analysis using the interpreted method signature whose name is
equal to `name` as the analysis entry point. For example, when analyzing
a script that uses `@main` to specify the entry point, it would be
convenient to specify `analyze_from_definitions = :main`.

src/toplevel/virtualprocess.jl

@@ -127,16 +127,20 @@ These configurations will be active for all the top-level entries explained in t
   If `true`, automatically set the [`target_modules`](@ref result-config) configuration so that
   JET filters out errors that are reported within modules that JET doesn't analyze directly.
 ---
-- `analyze_from_definitions::Bool = false` \\
+- `analyze_from_definitions::Union{Bool,Symbol} = false` \\
   If `true`, JET will start analysis using signatures of top-level definitions (e.g. method signatures),
   after the top-level interpretation has been done (unless no serious top-level error has
   happened, like errors involved within a macro expansion).
-
   This can be handy when you want to analyze a package, which usually contains only definitions
   but not their usages (i.e. top-level callsites).
   With this option, JET can enter analysis just with method or type definitions, and we don't
   need to pass a file that uses the target package.
 
+  When `analyze_from_definitions` is specified as `name::Symbol`, JET starts its analysis
+  using the interpreted method signature whose name is equal to `name` as the analysis entry
+  point. For example, when analyzing a script that uses `@main` to specify the entry point,
+  it would be convenient to specify `analyze_from_definitions = :main`.
+
   !!! warning
       This feature is very experimental at this point, and you may face lots of false positive
       errors, especially when trying to analyze a big package with lots of dependencies.
@@ -279,14 +283,14 @@ These configurations will be active for all the top-level entries explained in t
 struct ToplevelConfig
     pkgid::Union{Nothing,Base.PkgId}
     context::Module
-    analyze_from_definitions::Bool
+    analyze_from_definitions::Union{Bool,Symbol}
     concretization_patterns::Vector{Any}
     virtualize::Bool
     toplevel_logger # ::Union{Nothing,IO}
     function ToplevelConfig(
         pkgid::Union{Nothing,Base.PkgId} = nothing;
         context::Module = Main,
-        analyze_from_definitions::Bool = false,
+        analyze_from_definitions::Union{Bool,Symbol} = false,
         concretization_patterns = Any[],
         virtualize::Bool = true,
         toplevel_logger::Union{Nothing,IO} = nothing,
@@ -308,6 +312,8 @@ struct ToplevelConfig
     end
 end
 
+should_analyze_from_definitions(config::ToplevelConfig) = config.analyze_from_definitions !== false
+
 default_concretization_patterns() = (
     # concretize type aliases
     # https://github.com/aviatesk/JET.jl/issues/237
@@ -440,7 +446,7 @@ function virtual_process(x::Union{AbstractString,Expr},
     end
 
     # analyze collected signatures unless critical error happened
-    if config.analyze_from_definitions && isempty(res.toplevel_error_reports)
+    if should_analyze_from_definitions(config) && isempty(res.toplevel_error_reports)
         analyze_from_definitions!(analyzer, res, config)
     end
 
@@ -522,14 +528,17 @@ function analyze_from_definitions!(analyzer::AbstractAnalyzer, res::VirtualProce
     else
         analyzer = AbstractAnalyzer(analyzer, state)
     end
+    entrypoint = config.analyze_from_definitions
     for (i, tt) in enumerate(res.toplevel_signatures)
         match = Base._which(tt;
             # NOTE use the latest world counter with `method_table(analyzer)` unwrapped,
             # otherwise it may use a world counter when this method isn't defined yet
             method_table=unwrap_method_table(CC.method_table(analyzer)),
             world=new_world,
             raise=false)
-        if match !== nothing
+        if match !== nothing && (
+            !(entrypoint isa Symbol)#=implies analyze_from_definitions === true=# ||
+            match.method.name === entrypoint)
             succeeded[] += 1
             with_toplevel_logger(config; pre=clearline) do @nospecialize(io)
                 (i == n ? println : print)(io, "analyzing from top-level definitions ($(succeeded[])/$n)")
@@ -1303,21 +1312,26 @@ function JuliaInterpreter.step_expr!(interp::ConcreteInterpreter, frame::Frame,
 
     res = @invoke JuliaInterpreter.step_expr!(interp::Any, frame::Any, node::Any, true::Bool)
 
-    interp.config.analyze_from_definitions && collect_toplevel_signature!(interp, frame, node)
+    should_analyze_from_definitions(interp.config) && collect_toplevel_signature!(interp, frame, node)
 
     return res
 end
 
 function collect_toplevel_signature!(interp::ConcreteInterpreter, frame::Frame, @nospecialize(node))
-    if isexpr(node, :method, 3)
-        sigs = node.args[2]
-        atype_params, sparams, #=linenode=#_ =
-            JuliaInterpreter.@lookup(JuliaInterpreter.moduleof(frame), frame, sigs)::SimpleVector
-        tt = form_method_signature(atype_params::SimpleVector, sparams::SimpleVector)
-        @assert !CC.has_free_typevars(tt) "free type variable left in toplevel_signatures"
-        push!(interp.res.toplevel_signatures, tt)
+    isexpr(node, :method, 3) || return nothing
+    entrypoint = interp.config.analyze_from_definitions
+    if entrypoint isa Symbol
+        methname = node.args[1]
+        if !(methname isa Symbol && methname === entrypoint)
+            return nothing
+        end
     end
-    return nothing
+    sigs = node.args[2]
+    atype_params, sparams, #=linenode=#_ =
+        JuliaInterpreter.@lookup(JuliaInterpreter.moduleof(frame), frame, sigs)::SimpleVector
+    tt = form_method_signature(atype_params::SimpleVector, sparams::SimpleVector)
+    @assert !CC.has_free_typevars(tt) "free type variable left in toplevel_signatures"
+    push!(interp.res.toplevel_signatures, tt)
 end
 
 # form a method signature from the first and second parameters of lowered `:method` expression

test/toplevel/test_virtualprocess.jl

@@ -1577,7 +1577,7 @@ end
     end
 end
 
-@testset "`analyze_from_definitions`" begin
+@testset "`analyze_from_definitions=true`" begin
     let res = @analyze_toplevel analyze_from_definitions=false begin
             foo() = return undefvar
         end
@@ -1675,6 +1675,37 @@ end
     end
 end
 
+@testset "`analyze_from_definitions=name::Symbol`" begin
+    let res = @analyze_toplevel analyze_from_definitions=:entryfunc begin
+            entryfunc() = undefvar
+        end
+        let r = only(res.res.inference_error_reports)
+            @test is_global_undef_var(r, :undefvar)
+        end
+    end
+    # test used together with `@main`
+    @static if isdefined(@__MODULE__, Symbol("@main"))
+    let res = @analyze_toplevel analyze_from_definitions=:main begin
+            (@main)(args) = println("hello main: ", join(undefvar))
+        end
+        let r = only(res.res.inference_error_reports)
+            @test is_global_undef_var(r, :undefvar)
+        end
+    end
+    let res = @analyze_toplevel analyze_from_definitions=:main begin
+            module SomeApp
+            export main
+            (@main)(args) = println("hello main: ", join(undefvar))
+            end
+            using .SomeApp
+        end
+        let r = only(res.res.inference_error_reports)
+            @test is_global_undef_var(r, :undefvar)
+        end
+    end
+    end # @static if
+end
+
 @testset "top-level statement selection" begin
     # simplest example
     let # global function