1 files changed, 182 insertions, 0 deletions
diff --git a/tests/concepts/texplain.nim b/tests/concepts/texplain.nim
new file mode 100644
index 000000000..8cf04ae82
--- /dev/null
+++ b/tests/concepts/texplain.nim
@@ -0,0 +1,182 @@
+discard """
+  cmd: "nim c --verbosity:0 --colors:off $file"
+  nimout: '''
+texplain.nim(162, 10) Hint: Non-matching candidates for e(y)
+proc e(i: int): int
+  first type mismatch at position: 1
+  required type for i: int
+  but expression 'y' is of type: MatchingType
+
+texplain.nim(165, 7) Hint: Non-matching candidates for e(10)
+proc e(o: ExplainedConcept): int
+  first type mismatch at position: 1
+  required type for o: ExplainedConcept
+  but expression '10' is of type: int literal(10)
+texplain.nim(128, 6) ExplainedConcept: undeclared field: 'foo'
+texplain.nim(128, 5) ExplainedConcept: concept predicate failed
+texplain.nim(129, 6) ExplainedConcept: undeclared field: 'bar'
+texplain.nim(128, 5) ExplainedConcept: concept predicate failed
+
+texplain.nim(168, 10) Hint: Non-matching candidates for e(10)
+proc e(o: ExplainedConcept): int
+  first type mismatch at position: 1
+  required type for o: ExplainedConcept
+  but expression '10' is of type: int literal(10)
+texplain.nim(128, 6) ExplainedConcept: undeclared field: 'foo'
+texplain.nim(128, 5) ExplainedConcept: concept predicate failed
+texplain.nim(129, 6) ExplainedConcept: undeclared field: 'bar'
+texplain.nim(128, 5) ExplainedConcept: concept predicate failed
+
+texplain.nim(172, 20) Error: type mismatch: got <NonMatchingType>
+but expected one of:
+proc e(i: int): int
+  first type mismatch at position: 1
+  required type for i: int
+  but expression 'n' is of type: NonMatchingType
+proc e(o: ExplainedConcept): int
+  first type mismatch at position: 1
+  required type for o: ExplainedConcept
+  but expression 'n' is of type: NonMatchingType
+texplain.nim(172, 9) template/generic instantiation of `assert` from here
+texplain.nim(128, 5) ExplainedConcept: concept predicate failed
+
+expression: e(n)
+texplain.nim(173, 20) Error: type mismatch: got <NonMatchingType>
+but expected one of:
+proc r(i: string): int
+  first type mismatch at position: 1
+  required type for i: string
+  but expression 'n' is of type: NonMatchingType
+proc r(o: RegularConcept): int
+  first type mismatch at position: 1
+  required type for o: RegularConcept
+  but expression 'n' is of type: NonMatchingType
+texplain.nim(173, 9) template/generic instantiation of `assert` from here
+texplain.nim(132, 5) RegularConcept: concept predicate failed
+proc r[T](a: SomeNumber; b: T; c: auto)
+  first type mismatch at position: 1
+  required type for a: SomeNumber
+  but expression 'n' is of type: NonMatchingType
+
+expression: r(n)
+texplain.nim(174, 20) Hint: Non-matching candidates for r(y)
+proc r(i: string): int
+  first type mismatch at position: 1
+  required type for i: string
+  but expression 'y' is of type: MatchingType
+proc r[T](a: SomeNumber; b: T; c: auto)
+  first type mismatch at position: 1
+  required type for a: SomeNumber
+  but expression 'y' is of type: MatchingType
+
+texplain.nim(182, 2) Error: type mismatch: got <MatchingType>
+but expected one of:
+proc f(o: NestedConcept)
+  first type mismatch at position: 1
+  required type for o: NestedConcept
+  but expression 'y' is of type: MatchingType
+texplain.nim(132, 6) RegularConcept: undeclared field: 'foo'
+texplain.nim(132, 5) RegularConcept: concept predicate failed
+texplain.nim(133, 6) RegularConcept: undeclared field: 'bar'
+texplain.nim(132, 5) RegularConcept: concept predicate failed
+texplain.nim(136, 5) NestedConcept: concept predicate failed
+
+expression: f(y)'''
+  errormsg: "type mismatch: got <MatchingType>"
+"""
+
+
+
+# proc r[T](a: SomeNumber; b: T; c: auto)
+# proc r(i: string): int
+# proc r(o: RegularConcept): int
+
+
+
+
+
+
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+
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+
+
+# line 124 HERE
+
+type
+  ExplainedConcept {.explain.} = concept o
+    o.foo is int
+    o.bar is string
+
+  RegularConcept = concept o
+    o.foo is int
+    o.bar is string
+
+  NestedConcept = concept o
+    o.foo is RegularConcept
+
+  NonMatchingType = object
+    foo: int
+    bar: int
+
+  MatchingType = object
+    foo: int
+    bar: string
+
+proc e(o: ExplainedConcept): int = 1
+proc e(i: int): int = i
+
+proc r[T](a: SomeNumber, b: T, c: auto) = discard
+proc r(o: RegularConcept): int = 1
+proc r(i: string): int = 1
+
+proc f(o: NestedConcept) = discard
+
+var n = NonMatchingType(foo: 10, bar: 20)
+var y = MatchingType(foo: 10, bar: "bar")
+
+# no diagnostic here:
+discard e(y)
+
+# explain that e(int) doesn't match
+discard e(y) {.explain.}
+
+# explain that e(ExplainedConcept) doesn't match
+echo(e(10) {.explain.}, 20)
+
+# explain that e(ExplainedConcept) doesn't again
+discard e(10)
+
+static:
+  # provide diagnostics why the compile block failed
+  assert(compiles(e(n)) {.explain.} == false)
+  assert(compiles(r(n)) {.explain.} == false)
+  assert(compiles(r(y)) {.explain.} == true)
+
+  # these should not produce any output
+  assert(compiles(r(10)) == false)
+  assert(compiles(e(10)) == true)
+
+# finally, provide multiple nested explanations for failed matching
+# of regular concepts, even when the explain pragma is not used
+f(y)